You also have to consider what the joint is for. A dovetail joint is designed to be strong in a particular direction - resisting pulling apart against the wedge of the dovetails. It's not as strong when being pulled in the other direction, and the wedge shape of the tails and pins may even make it easier to collapse in the diagonal force direction that you applied. If you were to retest with a 90° pulling force instead of a 45° pushing force, your results would definitely change because the mechanical advantage of the dovetail would actually play a factor.
You remind me of when I pointed out to the one gentleman he tried to Say end grain to end grain glue up with stronger than long grain to long grain. But his test was flawed by the direction he was applying the force. As I explain to him if you were making a stool that was 1‘ x 2‘ you would put the grain running the 2 foot length. Now if you cut that stool and a half across the grain and just glued it up would you trust the stool to stand on? I wouldn’t now cut that stool instead of across the grain with the grain and then glue it back together now would you trust the stool? Yes I would. Which direction the grain runs is part of Woodworking that makes your end project strong if you do it right but weak if you do it wrong.
Two women in a thread in a male dominated job subject, and being smart and relevant - my toxic masculinity is triggered and offended.. Keep it up ladies. ;)
Strongest joint I've seen is also a type of miter joint. The lock miter joint, machined on the shaper, has outstanding strength due to the glue surface area. I also couldn't help but wonder, would the tyloses in the white oak have made a difference by not allowing the glue to penetrate the pores?
I wonder how a pocket miter would do. I have often used those for small projects. Now that the miter and pocket were both pretty high on his list, what would combining them do?
Seriously, your dovetail was crafted by an expert. I'm sorry, the small contrasted with large dovetails is ignorant. The small dovetails will obviously break. Go back to structural engineering classes.
My theory on the dove tail is that the pins were just too small. Your box joint beats it just by having more glue area. I think you could get a significant boost with a 50 50 ratio of pin to tail
This. It was a pretty bad example of a dovetail joint. I questioned it on first glance, and not surprise it failed spectacularly. The little details make a huge impact. Also you have to account of the same wood and same glue, which he didn't. You can also cut dovetail joints in the trans-axis/dimension, which would decrease it's rigidity in the "pulling direction" but increase it in the "crushing direction". There's some interesting techniques in Ancient Japanese woodwork, and they occasionally used spines which really adds a lot of strength. That was no surprise to me. Before the video here's how I expected it to go: 13- Butt Joint Glued 12- Lamello Attached 11- Domino Attached 10- Milter Joint 9- Dowel Pins Embedded 8- Pocket Hole Inside 7- Pocket Hole Outside 6- Butt Joint with nails 5- Butt Joint with screws 4- Milter with spines 3- Box Joint Proper 2- Dovetail proper 1- Dovetail 3D/spines 0 - Weld that sucker!
@@shadowanonymous3941 Dovetail joints present a lot of areas for stress concentrations. Stress concentrations in a linearly grained material can cause failures like this. I do agree that the small pin size may be a contributing failure factor, I would expect more equally sized pins/tails to be stronger in a situation like this.
Not so much the glue area, it simply slid . And with the angled cut it should have actually offered more surface area than a straight cut in a box joint. It most likely slid thru because of the angle of the cut and that was simply limited by the thickness of the pins (thinner material means you cannot increase your angle on both sides. The thicker box joint mainly offered a compression force distributed to both sides of each pin. The thin pins cannot simply be compressed on both sides to prevent it from sliding. That is, given that the pins have very tight fit. It could simply be that the dovetail pins were not as tight as the box joint. The fact that it slid instead of breaking at the shoulder means there is a problem with the fit. Of course, given the forces applied, the box joint will always defeat the dovetail in terms of preventing breaks at the shoulders since the grains are simply supported on all sides unlike the angles cut on a dovetail where the pins are smaller in diameter closer to the shoulder.
No, it's because dovetails are specifically strong against pulling pressure, not 45 degrees downward pressure. If it was a pull test, dovetails would be top.
As an engineer specifically in structures, the applied force and direction in relation to the joint have a huge impact on the results. The joint actually felt more force than the weight you put on top. This is called a moment arm between the joint and applied force. This is measured perpendicular from the joint and the applied force. I agree with you that more test would need performed as this is one case out of several cases and only measures the strength of these joints in a very specific instance. Still fun to watch and interesting.
While true, the measurement of the force in pounds isn't really important here. What's more important is the comparative data - Having 5-10 of each joint would be helpful to take an average reading of the breaking-point of the joint. Also, instead of a levered arm with gym weights, using a hydraulic press with a more accurate digital readout would provide more accurate comparative readings. This is a good start, for sure.
Side topic from the video. Don’t have a degree in this field, but use moments, arm, and center of gravity (CG) all the time for work. If you would be willing to help us understand more. Wouldn’t you have to figure the moments being applied by finding the distance from the joint (arm) and then find the CG and multiplying them? You just used the term “moment arm” and I’ve always thought those as two separate things.
A better measure for the strength would be the torque in the joint. This depends on the force applied, the length of the lever and the angle between the direction of the force and the lever. Sometimes torque is also called moment which someone else here mentioned, so maybe we're talking about the same thing. Consider using torque to compare with new measurements or just keep the setup unchanged. Great video and what a surprising result!
I would love to see this test done a second time with the same wood and joints, but this time testing the breakage in a pulling direction. As several already mentioned in the comments, different joints are strong in different aspects, and depending on what you're constructing you may need some joint over other. In physics, we call these different loads *compression* (what was tested in the video) and *tension* (if we pulled the ends apart). We also have *torsion* (by twisting the joint) and *shear loads* (by dislocating one board out from the plane of the ∟-shape), that would be interesting to look at. The differences in these strengths are actually quite important in fabrication. For example, if we were to construct a box (with no top or bottom) using only Miter joints we would now expect this box to be super strong from what we just learnt. But this is not necessarily the case.. If we try to crush this box (by for example by standing on its edge), only two of the box's joints will be under compression (the two joints on the side). The other two joints (the top and bottom joints) will actually be under tension. So if the Miter joint happen to be very weak under tension, then the box will break pretty easy, even though the Miter joints are super strong in compression.
Wouldn't every joint here actually be tension and / or shear though? The inside corner of the joint in each case provides a fulcrum around which the joint fails. The box joint is basically just a bunch of glue joints failing in shear.
I was thinking the same thing. He could just take the joined boards and rest them on a level, low-friction surface in an inverted vee (^) shape, then apply a straight-down vertical force to the joint.
@@crackedemerald4930 This was the first thing I thought of - 1 sample per joint is suggestive but not definitive, and it would have been a lot better to have a whole bunch of each joint. But he has limited amounts of time and funds. It'd be great, though, for a senior thesis in woodworking engineering, to have repeated tests. He could also have tested other types of joints (that I just listed in a comment of my own).
As a completely non-woodworker I definitely guessed the splines and was pleased my guess was correct. My thought process was that the way your contraption was setup is that it emphasizes compression on the inside of the joint which translates to tension on the outside of the joint. So I assumed those splines would be best to resist that tension since they are full grain wood running the exact direction of the tension.
Excellent analysis! This is the type of logical thinking I wish I'd see more of in woodworking. As Donny P said, most woodworkers seem to have very little understanding of these things.
im 16 never done woodworking in my life randomly watching this. And instantly knew the splines would win because the wood is going the same direction as the force. Like its hard to tear a pice of wood by pulling on it or i n this case compresing. idk
An excellent video that triggered a storm of responses and professional opinions. Wow! IMO, your practical experiments taught us all a helluva lot ... grain, surface area, geometry, glue, the value of trial and error ... a thoughtful human effort. Thank you for your hard work!
Great test!! But the very first test, butt joint, and simple mitre. I worked in a custom mill shop most of my life and we found when gluing them, glue up the joint, put together and let it set for about 10-15 minutes without clamps etc. Then we released the pieces and added another layer of glue, then clamped it, WHAT A DIFFERENCE in strength!! Back when the moldings were applied to cabinet door and drawer fronts we never nailed anything, just glued with small hand clamps and with drawers and cabinets always slamming shut we NEVER had problems. DOUBLE GLUE!!
A lot of good suggestions in the comments. One thing I would add, it would be more beneficial to do multiple tests of each joint. It is entirely possible that one or more of the joints failed earlier than a typical example of that joint, and it is also possible that one or more were hero joints, holding on longer than a typical example of that joint. I know it is more work and cost to make and test multiples, but it would help to establish more reliable results.
I had this thought, too. He put so much effort into this, so I don’t want to seem flippant, and you don’t seem flippant to me, to be sure, but IMHO science would require multiple (at least 3) examples of each to test just because, like you say, any one of those joints could’ve been a lemon. This kind of research is absolutely awesome, though, and hats off to this guy for making it happen.
Agree. There's a video about glue strength that did 3 of each and sometimes there was pretty big sample to sample variance. Maybe he just got a bad dovetail :)
@@Bob.Silverstein I don't know if you remember this, but about 10 years ago, there was this meme floating around of a child's science experiment where she fed one plant tap water and the another plant water that had been heated in a microwave oven, then allowed to cool. The one watered with the microwave-heated-then-cooled water died while the other one flourished. So a lot of people started to avoid using the microwave! Follow-up studies were significantly less viral, unfortunately, but they sampled a lot more plants and it turns out the kid just had a bad plant that wan't going to make it anyway - and it happened to be the one that got the microwave water. So, anyway, I'm speaking to the choir here. It would triple the time and resources required for his experiment and if I was him, my eyes would be rolling, so I also want to emphasize - I really appreciate this video and the spirit in which it was produced.
@@sivacrom agree on the extra time taken being pretty steep. But perhaps it would be worth picking six of them: butt, miter, spline miter, box, dovetail, outside pocket screw. Another thing I didn't even think of is that it might differ for hardwood and softwood for a variety of reasons. Softwood might take glue better. Hardwood might support screws better. So one could get very different results with pine versus oak.
@@sivacrom also, I do remember experiments like the one you mentioned. Not surprising. You could even show that singing to a plant causes it to grow twice as fast, if you have an N of 1 :)
Miter had me stunned! Thank you for running the gauntlet! Also, stray option that might help: Drill into the narrow edges of the box-joint, and plug with wooden dowel (imagine if you were making a 'hinge' out of wood, dowel plugging through each 'tooth' of the box-joint) to prevent the two boards from tilting out of alignment; it should force the inner dowel to fail, first, which'd be difficult in that confined bore.
I think the idea of the dovetail being so superior is that as it begins to come apart or loosen up (say in a really old drawer that’s been opened and shut A LOT) it still functions whereas a miter, box, or pocket hole are basically shot the moment they start to loosen up
I would like to see a Greene & Greene style box joint tested, one with dowels and one with screws. It's probably not as strong as a conventional box joint but I would like to see how it holds up compared to the others.
Would be cool to see how miter-lock joints would hold! Incidentally, I make my bee boxes with splined miters and they hold up better outdoors in the sun than the traditional box joints that most use. I didn't know it would be stronger but less end grain exposed to the elements seems like a good idea.
The strength of the miter joint is really surprinsing. A few thoughts on that: - Since your miter joint is 45 degree, and you placed it in a 45 degree angle, the strain is ideally angled, as the joint should "see" no to little shear stress. I wonder what happens, when you alter the force direction. - The surface area is around 40% greater than that of a simple butt joint. - The cutting surface is a mxiture of end grain and long grain. Could you do a test, where you presoak the endgrain in a mixture of water and glue, let it dry and then glue it? Super interesting video! I feel like such videos really bring reliable knowledge to the community!
Its not so much the angle. Technically its an arm of momentum thing where the inner corner is the centerpoint. Looking at that, it is important, that it is not only 40% more glue area, but the additional area is also at a larger distance to the center of rotation, giving it a much larger arm of momentum. If you calculate effect, you'll find, that those 40% can hold the same weight, as the first 100% So only from that effect, you could expect double weight. Adding those splines improves even more especially at the longest arm. Another interesting thing is, that this connection does not apply any stress onto the fibers, that separate them from each other (as happens in the butt joint) They are mainly and in a bunch pulled in their fiber direction. Really would like to see how it would perform if the glue surfaces are prepared (pre glued).
You want sheer stress in a test like that. Lap shears can resist a lot of force. The main problem here is the glue being used or the bond line that is generated is insufficient.
Another interesting thing with the 45° miter is the taper of the wood to the point of greatest tension. This helps to minimize peak tension stresses. This turns out to be more effective than shear stress in the other style joints.
The dovetails we used when I was making furniture, were more like your box joins in size and spacing, just dovetail shaped. Maybe the size and number made a difference. I think the big difference with this test is the amount of friction you can have versus tensile strength, maybe the ultimate joint would be the mitre with splines, but have the splines being evenly spaced and sized to the actual join wood, or at least increase the number of them. I have no idea really.
Its so funny that only you say it… we learned in school that it have to be in a specified ratio, so the gap cant be thin like in the video. Its look good but not as strong.
I don't understand the point of those dovetails where tails are thick and pins are thin. tails and pins should be about the same thickness as the thickness of the board or slightly wider. I'm not sure if it's done that way for esthetic reasons, but they don't look nice to my eyes.
Yeah, the thinnest part of the dovetails become the weakest link. Bigger splines don't do anything, they just add surface so more thin ones would be best, but not too many to make the wood in between them too thin.
agree. Seems the dovetail was too thin and we can see on the video that it was the timber that failed (because it was too thin) and not the joint or glue.
If you are still doing this.. try angling the outside splines in your mitre joint instead of all of them being parallel with your downward force. It could be as little as 10 degrees. Also, try some angled dowels as splines toward the inside of the joint. My theory is that the angles will transfer some of the downward force into other directions (namely into the wood itself) which would weaken the overall downward force applied to the joint. I also believe that there is an optimal degree of angle for maximum strength. Too high would be much less effective and would probably weaken the joint.
Also would be interesting to see how much the material used for the splines/dowels matters. It‘s likely that in softer/weaker woods, dowels and splines made of strong woods would have a greater impact on joint strength. I recently saw a gizmo for drilling dowels at opposite 45 degree angles (I think on 731 woodworks‘ channel?) which locks the joint together. Thought that was interesting. I‘ve seen many finish carpenters take that approach with moulding and brad nails, angling them opposite to lock it in, but hadn‘t seen it previously with dowels.
That was really cool. Now that I’ve seen it I can see several variables to consider. For the dovetail and box joints the strength would be affected by how tight the joints are. William Ng has talked about this in some of his videos. For wood glue to perform at its optimum strength it can’t be too tight or too loose of a joint. For the tenon, dowel, and spline joints the walnut splines likely we’re stronger than the dowels and tenons assuming those were just pine. And for any joints using end grain my high school shop teacher taught me a trick to make them stronger. I was building my Mom a bookcase out of hickory and due to time constraints I didn’t have time for fancy joinery to attach the top so it is just a butt joint where the top sits on top of the sides. He had me thin the wood glue with water and apply that to the end grain a couple of times and let it soak in without assembling the top, then after it was dry I came back with just glue and put it together and clamped over night. That was in 1975 and it has never failed in spite of being moved many times by lifting it by the top while fully loaded with books.
Dear Wendel, thanks for doing this test. It certainly revealed some surprises, particularly the dovetail joints. I built a bedroom suite 40+ years ago using veneered chipboard for the walls of the furniture modules. The only joint I could make easily was a mitre joint with glue. Despite decades of abuse, no sign of breakdown. I got it right way back then before your video {or computers or internet etc}. Cheers.
Loved watching thee tests and the method you used. The dovetail could have been starved of glue. To many people make an ultra tight joint. No room for adhesive. I spent a good part of my life as a Cabinetmaker. And made hundreds of dovetail drawers via a dovetail jig I made in the shop. I found that I needed a certain amount of slop so that there could be proper glue joint allowance. Too tight and I squeezed out all of the glue.
As a structural engineer that designs wood connections all the time, it would be really interesting to test the strength of something other than the glue. Some of those connections seemed quite strong if it weren’t for the “snap” of the glue bond failure. I’d love to see just how high you can go with things like truss plates, angles, and structural nails and screws. Obviously a carpenter isn’t making a cabinet to withstand an earthquake, but I think it would be fun either way.
All my cabinets and shelves seem to have withstood multiple earthquakes. Perhaps not good for their structural integrity but nothing has fallen apart,not even the antiques.
As interesting as that may be, I think it would get really silly really fast. Heck even this test showed that steel vs glue is no comparison. The pocket holes had 2 screws and it put them in 4th place even though there wasn't a lot of wood to hold them. Something like a truss plate, you instantly get to the point where you pretty much just find the weak spots in the wood. Which if you think about it makes sense. Its kinda why we invented truss plates lol. The only reason miter was so high was the leverage gain of having that glued plane being level.
Yup. That's why I just use glue, maybe pin joints if it's a bookshelf but most modern glues can handle what I can throw at it. Worst comes to worse yoy can always add support.
I would love to see the follow up video to this with more tests: • different sizes of dovetails/fingers • different wood glue uses • different woods and whether or not cross-hatching helps wood glue hold it tighter I liked and subbed!
Its pretty rare that a drawer or box is stressed that way. I would love to see these tests repeated as a pull test instead (think the pulling action on a drawer).
Yes please! Although I suspect that the miter with splines may still come out surprisingly well. I also wonder how much difference it would make if dowels and/or loose tenons (dominos) were perpendicular to the force applied to parallel to it. IOW which end of the box angle you pull on probably makes a difference. Another interesting test would be sheering force. Make a T like a shelf attached to the side of a cabinet. Apply downward force close to the joint. How do pocket holes, dominos and dowels compare to a dado & rabbet? (Hint: I’m pretty sure I know the answer.)
I'd like to see the test after the pieces have aged for a year or two. I suspect the miter would turn out to be one of the weakest joints. What we're seeing is the strength of fresh glue here, not of the joint.
Miter joint also significantly changes the angle at which the forces are transferred between the two boards. That could have an impact here. It's plausible that if forces were applied at different angles the miter joint would turn out not that great.
As a full time engineer and hobbyist wood worker this is a fantastic video. I will say that by applying the weight to a lever arm you're testing the torque on the joint rather than the weight that it can hold. But because each test piece is consistent you do get reliable results and eliminate quite a few variables. Great to see you invested in a lab coat as well for science!
Great comment! Lol. Lab coat! Most "Doctors " are the same. They just google what pills to give you for the symptoms NOT the actual cause. But that is for a different discussion. 😜😊
Yes, it's actually the law about force and lever action that applies. The cross-product of force and distance is torque. So what we needed in this experiment was the distance from the end of the board to the center of the joint thus calculating the actual force applied to that joint. The result would be a figure in Newton meter or Nm, not in pounds or kilogram. However, I think we should leave all the complications out of this equation and see it as a practical experiment or proof of concept. ;)
Yeah nah I wouldn't say it's torque. Because if you put the same weight further out from the pivot point it would still put the same force acting down on the joint. Or are you talking about the wood joint being the fulcrum? In any case, as you say, the experiment is consistent. It's comparing different joints under the same test conditions, and using the amount of weight on top as the variable.
@@Pan_Galactic_Gargle_Blaster it would only be torque if it was driven from a motor at the axis, or if a constant weight was at a constant distance and the force on the joint was at a different distance. Then you would talk about torque. But the weight is directly above the joint. It's always going to be the same amount of weight on the join if you have the weight directly above it, no matter how long the arm is. You could measure torque on the hinge, and that would change based on the arm, but the weight on the join is always going to be the amount of weight you put above it. He even showed this in the video.
Testing under a tensile load and testing fatigue strength to cyclical loading would probably have very different results and would be interesting to see
Thank you for doing this. I have some ideas for a project that specifically requires me to know what wood joints would be best. You saved me a lot of time
An interesting thing is that the splines can be added to a miter joint after the fact. One part of the strength of the miter is that it is end grain to end grain, and wood glue generally works best that way - as it seeps into the pores, it effectively makes tons of tiny glue dowels in every pore of the wood.
A point on dovetails, I've notice from looking at my late Grandma's 100 yr old furniture. Dovetails are everywhere, but there is zero glue. Seems to me that dovetails were not developed to be a strong joint that stands up to compression force, but to stay together along a specific direction of force before glue was a thing that saved all mediocre wood workers (
There was definitely wood glue 100yr ago. Humans have been using glue for 70,000 years. Egyptians used glue for wood furniture 4,000 years ago. Your grandma just bought some junk, either missed the glue or used something low quality that deteriorated. Dovetails are definitely traditionally glued.
mechanical engineer: my take is that the way dovetails are hand cut left a stress concentration at the inner edge of the tail (see failure pic for where it split). this is where the saw stops when hand cutting the tails. routing the dovetail would likely do a little better job (similar to box joint). altho box joint would still be better since it is shearing the glue only and not exerting a force that is splitting the tails
One thing I'd add that I haven't seen mentioned yet: testing for max strength doesn't necessarily account for the effect that cyclic loading will have on a test joint - the goal with a drawer isn't to withstand a single incredibly forceful push/pull, it's to withstand pushes and pulls over the lifetime of the piece, as the materials age and as the piece undergoes varying environmental conditions. That's not to take anything away from this testing methodology. But rather, to point out that this test isn't going to give someone all the information they might need to select a joint design for a project. More specifically, I don't think it's reasonable to conclude from this test alone that dovetails are mostly for aesthetics. Beyond that, other people already mentioned the difference between static and dynamic loading, and I would emphasize that: it would be good to control for _how_ you apply the weight, to make sure that you're not (for instance) dropping the weight more when you're worried about a high stack of weights toppling onto your foot. Someone else has mentioned using a forcing screw, and I know Matthias Wandel already uses one for his experiments. Something like that would be a much more repeatable way to load the joint.
I've found that while butt joints offer more than enough strength in a single instance, the repeated strain of opening and closing the drawer tended to cause failure over time... but this was still a valuable and interesting video, thanks as always for posting!
I knew the miter joint would be in the top 3 because it increases the surface area by the greatest amount AND in the same direction, i.e. in line with the grain. In 3/4" wood it's about 1" high by whatever the width of the wood is. I use this for building speaker cabinets, and I was originally surprised at how strong it is - especially when it's a box and not just two boards. The dovetail and box joints actually reduce the effective surface area quite a bit; in the context of this test, the sides of the fingers provide little to no structural integrity because the force would be torquing on them rather than pushing or pulling.
I'd like to see a mortise and wedged through-tenon setup (not dominoes) for the next go around. I suspect it would out-perform the dominoes and dowels, but it would be interesting to see the results. With that joint, the wood should break before the joint, if done correctly. That's been my experience with them anyway. Also, how do you NOT have a dovetail jig in that shop? Seriously. You literally have all this stuff nobody has ever heard of, but you have to outsource a dovetail? That alone may have blown my mind more than the test results. Anyway, really enjoyed this. Looking forward to round 2!!
A corner joint such as being tested here, is not the correct application for a through mortise and tenon. It would not be strong at all. The end grain of the one piece of wood would just blow out.
As far as I can tell, the boxjoint (fingerjoint) was stronger than the dovetails, cause they were too delecate and thinn. If you’d made them more even in width or made more dovetails (5/4 or more instead of 4/3), like on the boxjoint it would have held more lbs.
Dovetail is a fundamentally flawed joint type. Reguardless of the size or amount of em. All the pressure from the weight ends up on that small short "triangle" shape at the sides of each dovetail. So just as you saw, the wood will break on that triangle line leaving one side looking as if it was a box joint because that small wood section ends up as the weakest part of it making it much weaker than a normal box joint.
Thank you very much for these tests! 👍👍👍 If it can help francophone to have an overview of the results : - Joint basique (de bout) : 27 kg - Joint lamello : 32 kg - Joint domino : 45 kg - Joint avec vis noyées en biais (type Kreg) placées à l'intérieur : 50 kg - Joint avec tourillons : 50 kg - Joints avec assemblage à queue d'arronde : 50 kg - Joint avec vis noyées en biais (type Kreg) placées à l'extérieur : 77 kg - Joint à simple coupe d'onglet 45° : 95 kg (!) - Joint à queue droite : 100 kg - Joint à clés d'angle : 120 kg
The dovetail wedge shape splits the wood in half due to the loading, that's why it's weaker than the box joint. It's strong in tension, not rotational loading
The thickness of the top of the pins and the angle of the dovetails matter alot as well. I always make my dovetails with half an inch at the tap of the pins if structure matters at all. I'd like to see a dovetail angle shootout one of these days.
The thin pins is what had the dovetail fail .. someone should recreate this test with a dovetail /pin 1:1 size ratio ..those thin pins looked nice but didn't provide strength .
The glue surface area is part of it, you're getting (I think) 1.4x the surface area. There's also the question of leverage. The inner corner of the joint is the fulcrum, with the board is one side of the lever and the outside corner is the other side of the lever. By using the 45 degree cut, the short lever (the joint) is lengthened by 1.4x. I was surprised it made that much of a difference, though.
Agreed, this is the way I would flex the joint to break it but also not how mitered joints on a drawer are used so I'm not sure the examples are applicable to the the intended end use they were designed for. Also all joints were glued and some designs were developed to be used without glue at all. I'd like to see that basic mitre joint hold up to its own weight even without glue! The other problem with using glue is that this just becomes a test of which joint has the most surface area along the long grain of the wood. And for that it could have been simply mathematically calculated without even testing and probably predicted fairly close results to this.
The miter joint is surprisingly strong in this direction for both of the reasons you listed, and two additional ones: 1) It's actually more like an edge-grain bond than you'd expect. And edge grain bonds are all about surface area. 2) Wood glue is stronger than many woods IN TENSION, not in shear - this is why the miter out performed the box joint - it's all about how much glue you can get in tension when you load the joint up.
Mathematically the leverage effect amplifies the whole thing to hold factor 2 instead of 1.4. so there must be something more. And I guess that is the direction of load on the fibers. A butt joint with that "leverage" load, actually pulls the fibers of the long grain wood apart from each other. In that direction the wood is very weak. If the force had a direction parallel to the fibers (which would be typical for that type of joint) they would have hold much much more. For that specific load shown here (which you try to avoid in ANY construction by creating triangles) the miter joint loads all fibers in their strongest direction, which gives the additional strength compared to others. That is, why the test is on one hand very interesting indeed, but of limited help to woodworking, as the direction of the force is very important. Even a butt joint has two different strengths depending on the direction you load them (parallel or perpendicular to the glue surface)
Ya, hopefully people don't start making drawers with miters because of this, lol. While this video was cool, the test was more or less irrelevant. The vector of the force was different than a push/pull force a drawer would receive. For a miter join, the glue would take all that repeated force over years which would inevitably lead to a failure. The dovetail, however, is distributing that force to wood-on-wood contact. Meaning, for the joint to fail the wood itself *must* break. You don't even need glue for a solid dovetail join. Fun test, fun video, but ultimately "wrong" and misleading.
@@JustinSmith1287 I don't see the miter joint failing at all on a drawer if you add splines. The joint is so simple it shouldn't work so good, but apparently it does.
One more consideration is the impact of the joint ‘failure’. Some of these options fail catastrophically, others (particularly the pocket screws) would hang on as a kind of hinge.
Also the ease of repair though. If a glue but joint fails, you can often just reglue it and you‘re good to go (after sanding off the remaining glue, provided it broke on the glue joint and didn‘t destroy the wood too much). With failing pocket screws, it can really tear up the wood.
I always found that applying a layer of glue on end grain and allowing it to dry to tacky then apply a second layer and affixing the joint it results in a much stronger bond. The initial layer will absorb into the end grain and the second layer will bond to the first and both boards. You then have a very deep glue bond to the end grain board. It would also be interesting to do the same round of tests using two part epoxy resin and see the performance difference compared to wood glue. While I know it’s generally not feasible to use epoxy for most wood projects nor is it necessary to have that much strength, I think the results would be surprising. I used to make custom knives and used Smooth On epoxy for handle retention with dowel pins as the mechanical connection. Since most of the knives I made were bushcraft knives and would be put under serious use, from chopping and batonning and occasionally throwing, the handles needed to withstand enormous amounts of shock force.
Wendel did these tests a decade ago and determined with some confidence that the only thing that matters is total joint surface area with glue. The strongest joint will be a box joint with many, many cuts to produce a lot of surface area.
Awesome test and wonderful neutrality. I guessed it right! I figured the splines would essentially act as struts for a triangulated joint. Right, my pick a stronger joint would be: Box, with a dowel run longitudinally through the assembled joint. So visually it looks like a hinge pin. Just need a long drill bit! (I just made that joint up in my head.)
Great video, very interesting. I'm a retired carpenter and I briefly studied Japanese joinery about 40 years ago. They use incredibly intricate joinery that has to withstand earthquakes. I was buying Japanese shark tooth pull saws years before they became popular here in North America. We had one time use feather files for sharpening them. They also use slip joints so that during an earthquake the joints don't snap and break they move around.
Unbelieveable! Virtually every drawer in my shop is made with box joints. 1000's of cuts. I am going to switch to the splined miter for all my future drawers. I need about 50 in the kitchen remodel I am doing and this will save me HOURS of time. Great test.
Great video! For some reason I suspected mitre joints to be rather strong, not simply because they have more surface area to hold glue, but because they convert the pressure on the joint to compressive force entirely eliminating torsional and shearing forces where the glue can best resist. but I never guessed they'd be THAT strong. There's one joint I presently go to more than any other; it's a locking mitre. For solid wood, I just use the router bit. For veneered plywood, I use the table saw, dividing the thickness into thirds, use the inside two thirds to create a locking dado, leaving the last third mitred. (Obviously, this is easiest using 3/4-in plywood.) It hides the plywood core completely leaving a finished corner inside and out, and I can orient the joint to oppose the direction of greater stress, and so far, they seem to hold an incredible amount of weight. I'd be excited now to see how well these test. Thank-you for this video.
Great video!!! When you redo the video, use Titebond III, it supposedly has a higher strength rating. Also TB1 & TB2 both tend to be far more brittle when fully cured, while TBIII can flex when cured which means it 'should' hold better & longer. As soon as I saw the thin pins on the dovetail, I immediately thought that it would not perform well. Looked to me like the dovetail board cracked then just separated, though honestly, I expected those thin pins to break off instead.
I agree with many of the other comments. As an engineer, I would like to suggest you an interesting upgrade for the test bench. Usually those tests are considered almost static while adding many pounds with weights isn't. I would add a screw to push the test piece: doing it slowly will make the results more precise (also more than one test is better, for engineering results we do 15 tests).
Funny how you dont comment on making 5-10 of each joint to rule out defects in the wood and produce some statistics. Also, standardizing the assembly procedure more to eliminate as many variables as possible would also help. Also, thirsty endgrain glue-up was the strongest joint, even though he kept saying it would be the weakest throughout the entire video. In my experience, end grain to end grain is the strongest when the glue is done like this: 1. Add glue. 2. Wait 5 or so minutes and add more glue. 3. Squeeze the joint together.
I love videos like this. Yeah there were a few things that could have been done better as mentioned in other comments, but in general, I learned something new. And that knowledge will come in handy when I go to do my own projects. Thank you for the informative video.
My ideas for a strong joints: -The 45° angle with thicker splines (similar to a box joint). Reason: It appeared as if the splines were actually the weak point. -Box joint but with a pin going through all of the pieces. The weak point of the box joint seemed to be the glue. So a pin should increase the strength by taking some of the load away. Another option would be to make the boxes narrower so the glued surface increases. That would of course combine well with the pin. If you want to be really fancy, you could try to reinforce that even more with some pocket hole screws. I think the possible strength of this is really just limited by the strength of the wood itself. -The spline thing but with deeper cuts so the splines actually go into the inside a bit. Another fancy way of doing this eould be to have bent splines so you are not dealing with pulling the grains apart.
I was buying wood at an Amish place once and they mentioned that mitered cuts almost acted like edge grain to edge grain. I was still surprised to see your results and still feel like a miter needs a spline.
I made a diploma frame for my son and did miter with splines. I wasn't sure if the splines would add much, but they looked pretty and I wanted to learn how to do it. Glad to know it might actually survive the inevitable dropping off the wall. I mean, he hung it right at the edge of his VR space. Thanks for opening up this Pandora's box of joinery. I wonder what kind of joints Pandora's box has.
Redo the dovetail. I'll explain. Yes it's the pin size to tail size. That style of dovetail is made for strength in pulling a drawer. Equal pin/tail sizes will be much stronger for the test you ran. Edit: also, increase the angle of slope to about 9° or 10° and make them half blind. You'll be suprised at where they end up. Probably top spot. Nice vid. Very informative.
I have a router bit for locking mitres I'd be interested in seeing tested. I suspect the locking mechanism is just to help alignment rather than strength, but it may increase the gluing surface by a percentage.
After seeing a previous comment about locked miters, I had to google the term to see what it meant. The first hit was for a router bit like you mention. It showed the resulting joint geometry, which led me to the same conclusions you mention: more alignment than strength, perhaps more gluing area, but not likely to add much strength as that geometry would just pull apart under the stress of this test [minimal extra strength at 2 or 3 very small points in the "key"], mostly subject to the additional glue strength.
That was a great experiment. I have to admit that I had the miter joint not lasting much longer than the butt joint, which I di have as the weakest. I also thought the dovetail with all of it's glue surface, and the cuts at angles would be stringer than the box joint. You learn something new everyday. Thanks for doing this!!
Great vid, Jason! If you do end up repeating this, I'd be real curious to see a lock miter joint included, especially since the mitered joint was so strong. Cheers!
Great video. I almost had the order right. The mitre surprised me for sure. I make cabinets everyday and only use box joints. Making sure to get a lot of glue on all surfaces...most will het squeezed out as you know on those tight fingers. I think the angle that the weight is applied to each joint could have an effect on the outcome. Hence the mitre would maybe be stronger or weaker depending on the direction the weight is pushing on the joint. Anyway thanks for the great video, I always wondered about different joints.
I'd like to see a test for the opposite direction of pressure. Clamping boards to something upright and placing the weight on the outer edge to test joint integrity. I think a few of them would fare better and a few worse.
The other great thing, you’re never going to be putting that kind of pressure on those joints at that kind of angle. But all around super surprising. I thought the miter would be SO much weaker!
This was great, thanks for doing it! After Patrick Sullivan's recent videos on glue strength (and the VERY surprising result for end grain) I was expecting the mitre to do far better than most would expect. And their good showing is a testament to how accurately you cut the joint, and how well you clamped, so extra kudos there. I was surprised about the plain butt joint, I thought that would do better than last place (even if the result does show it's not actually too weak to use); I honestly expected the Lamello to do slightly worse, because of the smaller glue surface area. Nerdy nitpick 🤓 the reinforcement in the winning joint, those aren't splines, they're keys. Splines run _along_ a joint, keys cross the joint (just like in butterfly keys). And yes yes yes, please do some follow-on tests 👍👍👍
@@tchevrier Yeah that's a great way of putting it 👍Did you catch how some sort hinted they already knew, or more directly stated that, "but......" But what? If you'd believed this before you'd already have content about it 😆 I bet it wouldn't be hard to go back through vids of many of the big names that responded and find direct proof they *didn't* think this was the case, stuff along the lines of _"I don't bother to put any glue on the end grain_ [in a dovetail] _because it adds no strength"_ _"90° butt joints need to be reinforced [because, end grain]"_ etc. I am pretty sure I've heard Cosman saying something related (although I haven't watched him in years so very vague memory), and maybe also Marc S., Sellers, Stumpy, Ramsay *and* Broun!
In wood aircraft construction, where the least wood / lightest weight, and greatest strength, are essential, joints are made by using glued internal corner blocks and exterior glued thin plywood plates that cover the joint. Nailed together. This gives tremendous resistance to the rotational force that you are applying.
The fact that the box and dovetail joints failed so perfectly at the glue points makes me think maybe they could withstand more with a better gluing job. My joints almost always fail at the wood and not the glue.
Funny thing about that. Wood glue is usually stonger than the "natural glue" the wood has to keep the fibres / grains in piece - the lignin. So a piece of wood is more likely to break along the grain than in the glue joint if the glue job is done right with good glue. That being said end grain glue joints should be stronger than side grain glue joints (cause the wood wont break across the grain before the glue does), given the glue is applied well enough!
Epoxy is superior to wood glue. This test shows in a few of these examples that the wood glue used is less strong than the wood itself. I agree using a superior and more consistent adhesive would make the test more interesting.
If you continue your science experiments I would love to see a comparison of smooth dowels, fluted dowels, spiral dowels, etc. I feel like there's probably minimal difference between them but it would be cool to see actual testing performed.
I agree. Having used Lamello joints using the wood bisquits i have found them stronger than dowels or splines (depending on wood types). The original Lamello joint is using angle grain compressed beechwood. Like the biscuits made by Lamello.
In one of my past lives I managed a mechanical test lab so this experiment was really exciting to watch. My only observation is that of your comment about the miter joint. Yes clearly, and surprisingly, it appears to be a very strong joint, but the unit of measure that you are really after is Torque which is load (weight) x Distance. The further away you place the load, the more torque you will have and therefore the total load that you will be able to place will be lower. But thus far, yours is the best video I have seen, good job!
I'm absolutely amazed by the miter joint! I've made a billion miter joint things and even had some break when dropped on the ground so . . . Just seems crazy.
Next time with your dovetail don’t make your tail so small. I know it’s part of the classical look of a dovetail whose primary design is to keep the wood from pulling apart after the glue fails. A lot of people don’t realize that the older glues sort of had a lifetime and then the joints would get loose and have to be re-glued together. Your Old hot glue’s just didn’t have the life expectancy of modern glues. Anyway with your next dovetail Make your tails and pins closer to the the same size so that it’s spaced closer to the spacing of the Box joint. I also noticed you didn’t do a proper through mortise or a mortise in a rabbit. I’m thinking the strongest version of a mortise and tenon joint you would start by cutting a rabbit at the end of one board and then notch out across that rabbit so you have protruding fingers like a box joint then in the other board cut matching square holes to be the mortises of your tenants. Your tenants would be about half the thickness of the board and depending on how many you make could be how about any width you want. And down for what I believe would be the strongest joint make a box joint but then drill a hole through all of the individual fingers top to bottom and put a thin hardwood dowel interlocking the fingers of your box joint. When it’s all done when you look at it from the sides it will look like a normal box joint but when you look at it from the top or bottom you will see the dowel down in the end of the board as a little circle.
@@johngray2875 And let’s not forget making those small itty-bitty pins is a weakness unto itself. Anyone can pretty much breaker matchstick it’s a lot harder to break a three-quarter inch board.
Yup, and conversely, making a modified box joint where the tails on one side are 1/8" thick would probably behave similarly to the (lovely) thin tail dovetailed board.
Dovetails are designed to be mechanically strong, in the direction of the joint. You applied a force in a direction that is 45 deg of the axis so the joint is less effective. Although, I can't be sure but I think the glue up needs to be more careful. The mortise and tenon is definitely one of the top strength joint, the Domino was not a good example, they were too small. I love my Domino machine so it's not a knock on the tool. I want to let you know how I appreciate you doing this.
So the miter joint with splines actually is quite aesthetic, especially with contrasting-colored splines. And given that it proves to be the strongest, woodsmiths should consider these to be a worthy alternative to box joints and dovetail joints.
It really depends on the application. Almost no project is going to be subject to the same type/direction of force in this video. If you're making drawers, the dovetail is going to be stronger, given the direction of the force you will be applying to it, than even the splined miter. If you're making a box that you will pick up often, with weight in it, the box and dovetail joints will be stronger as well.
I'd love to see this test done in the sheer/torsion direction - 90 degrees from how you had it. And see how the joints stack up there. Some might be better in that orientation.
That was extremely educational. I make mother joints all the time. I mostly put through dowels across the miter. That would be one to try. Oh and I use 1/4” dowels. I think that would be a good one for your next test. Great video as always
🤯 Wow! Absolutely insane! I was not expecting this result whatsoever. I love pocket holes and dowels. I thought a simple miter would have been the weakest. Thank you for taking the time to show us all of this. I've seen the splines before and just thought it was esthetics only. Now that I have a table saw, I really want to do splines. They are so pretty and now I've learned are strong too. I also learned that outside pocket holes are stronger. Did not know that. I thought they would have been the same result. Love your channel. Keep up the great work.
This is also a test of the glue, all joints have an increased glue surface over the previous one. Excluding the dovetail, even though the joint was well executed the ratio was a bit off for this test. Spacing the dovetails more like the box joint would have helped increasing its odds. There are so many different joints because they all serve different purposes.
The last sentence is the most important. Joints are meant to be strong at specific direction(s) and also handle twists, not just wait, and also to look nice.
Every single joint caused the glue to fail. His glue is the weak point in every single joint. He needs to try this with better glue to compare the difference in strength caused specifically by the joint.
I’ve always been lead to believe glue works best when cured under pressure. It would be interesting to see, glue under pressure vs. not. Dale Zimmerman of Franklin International, maker of Titebond woodworking glues, recommends 100 to 150 pounds per square inch (psi) for clamping softwoods and 175-250 psi for hardwoods.
I'm looking forward to the follow-up video! Also, I think the dovetail joint would have outmatched the finger joint if there were the same number of dovetails as there were fingers on the finger joint, and if the pins and tails were of similar size, instead of tiny pins and huge tails.
I'm a beginner and I was deciding what kind of joint I wanted to start practicing and this was helpful. For me and my equipment, it's the box joint. Now I'm going to watch your video on box joint and get ready to make my first box. It will be a Box Joint box. Maybe I make a smaller Box Joint Joint Box after that. With box hinges so it will be a box hinged, Box Joint Joint Box.
Quite an imaginative testing routine! I wonder how a more traditional "finger joint" might fare. Also I wonder at the lever action of pressing down on that 90 D joint. I dunno, but am not sure that most such joints are subjected to that sort of vectored and leveraged force. Might it be a more indicative test, to possibly subject the joints to lateral pulls - or possibly constructing a complete box using the same joint at all 4 locations, and then putting the pressure to the entire box with your inventive rig? Still and all, you've gotten my mind reconsidering what I thought I knew about the construction of various wood joints and joinery, which is what I think you intended in the first place. Many thanks!
Very useful thank you. I also read another comment that the resistance depends on the angle at which the pressure is received, that also makes sense. Greetings.
Kinda had a feeling that splines would win, simply for the fact of long grain glue up and that the breaking would have to cause the spline material either to overcome that long grain to long grain glue bond or it would have to rip apart which is in itself pretty hard to make happen for wood. Imagine if you would eliminate the weak point of this joint by adding more splines and make them a little thicker, that would have to make the glue joint come apart, which would be exciting to see the weight of having that to happen.
I thought the miter with splines would be 2nd or 3rd place. Surprised to see it at #1. I was also thinking about dovetail splines. I imagine those would be strong for several reasons -- glue surface, mechanical strength, grain direction, etc.
my grandfather always used miter with splines and I've always tended to use it as well. It's easy to do, looks great, and with contrasting wood, really shows off the joint. would have been happy if it only placed in the top 3 or 4... nice to see it show up at the strongest of the group. :)
I think the dovetails failed because they were not even Some of the tails were skinny and others fat. When you retest how about making them even like most people do. I love your videos and have learned so much. Thanks!!
Not at all surprised that miter with splines was first place, and it was my guess for first. I knew plain miter was going to outperform most people's expectations too, but still had it halfway down my list. Of course for that joint glue technique makes a huge difference, since you've got to make sure you use enough despite the end grain wicking it away. (I always apply, let sit for a moment, and apply again after it disappears.) Also miter with splines is my favorite aesthetically anyway. :D
I agree on the last point. It's one of the best looking. And I too thought he would have let the first layer of glue dry in the simple miter joint first, then add another bit of glue. Surprised he didn't do that.
Thx, you just made me feel a lot better about my short cut miter to make a support box for a small table top. I thought “oh it’s not very good but it’s only a 10x14 table 14 in high for my bathroom”.
I would be interested in what the results would be if you went with a dovetail mitre joint with spline and with the screws. Wonder if this combo could break the 500 lb mark.
Very interesting! I am a civil engineer and I would like to give a bit of info on the miter joint. Essentially, the force you are putting on, is put on the closest to orthogonal (the direction is closest to perpendicular) to the glued surface of all joints. With glue being best at pulling perpendicular to a surface, rather than having the shearing force of a less perpendicular joint, this is a great combination. Then lastly the miter joint has a greater gluing surface, allowing for an even higher pulling resistance. Its simple physics if you think about it, but it's not too obvious. In this test you basically only tested one direction of force. It might be interesting to test pulling force too, or a different pushing direction, I am almost certain the results will be quite different. With the right direction of force, the butt joint might even beat the miter joint.
I also heard a convincing argument that end grain is a BETTER gluing surface, provided it gets enough glue. Since the glue bond is stronger than the wood itself, the breakage of the wood is the real issue, and wood splits a lot easier than it breaks. Therefore, my theory is that the miter is stronger because it eliminates the surface straight ALONG the grain, and converts it to something closer to end grain that can't "split"
@@aaronfuzion I watched a glue comparison video in the past year or so that found End Grain glueups to actually be STRONGEER than Face Grain, which went against all previous recommendations. Perhaps the soaking of glue into the wood means the glue travels farther into the wood to provide more surface to adhere to? On the Miter joint, I think the physics part of it that BasTaart mentions is what is at play here and less about the end grain/face grain debate. While the board is trying to pull apart from the test, you have the inside portions of the joint pushing against each other acting as a small brace.
Great Video! Entertaining and informative. Very interesting results indeed. Based on other joint strength videos, I would have expected dowels to have been one of the stronger joints. You have used plain dowels. Maybe you could add an extra joint (in your suggested future joint tests) using fluted dowels? The extra surface area could make a difference and it would be interesting to see what the difference would be if any. Thank you
from the breakage, it looks like the dowel joint failed because it blew through the thin side wall. That suggests to me that the dowel to board ratio was too high. smaller diameter dowels would have done better.
I'd like to note that the differences between the dovetail and box joints has a lot to do with surface area and the glue. Early in the video the glue butt joint performed much better than expected. The smaller cutouts on the box joint had significantly more surface area for glue. I'd like to see tests where either the base or the end of the dovetail are equal to the box joint. I think that would pose some interesting results.
This is interesting! I NEED HELP to figure out what would be the strongest joint for a sturdy woodenbox to sit my refrigerator on. Top is. I want a top cover to attach to the sides of the box. Should I also put one on the bottom too? Thanks guys! :)
I would like to add , that the type & quality of the adhesive is an important & major factor in determining the strength of the joint. On the other hand, your demonstration is very impressive. As always, thanks.
My dad has been a finish carpenter for 40 years. I remember when he showed me how if you glue and clamp 2 pieces of wood and you went to break that piece of wood, it wouldn’t break on the glue seam. Wood glue is actually stronger than wood. Im assuming Mitre is strongest because you are glueing two identical pieces of wood/grain.
Great video! A couple of thoughts on the joints that surprised you: 1. Miter joint - this joint puts more surface area in contact because it's cut on the bias; more surface area = more strength. 2. Dovetail joint - the asymmetry of the tenon and mortise widths of the test joint makes me suspect that the smaller-cross- section tenons were the weak link. It would be interesting to compare strength of the style you tested to a more symmetrical one.
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It is also because you have endgrain to endgrain, when you have endgrain to longgrain the longgrain will splitt apart because it is pulled sideways. Endgrain to endgrain will pull the wood fibers in the correct direction. The splines added was made of walnut that is a stronger material. To make it correct it would need at least 10-32 joints of each, statistically sort out differences in wood and amount of glue.
It would be interesting to see the results of a dovetail joint that has the same number of pins and tails as the box joint did. Or at least closer to the same number.
I was thinking about that too. Also consider making the pins and tails roughly the same size. This is likely one of the reasons the box joint did so well.
@@stevesiefken6432 exactly. Who makes dovetails like the ones in this video? I know I've never done it that way. They're meant to be the same size. As soon as I saw those tiny dovetails I laughed.
@@popparock6506 The pins didn't break, though, so they weren't the weak point. The glue turned loose and allowed the pins to split their way out of the tails. There just needs to be more glue surface so the glue has more strength overall. With so little pin-tail surfaces touching, the glue joint was barely better than a butt joint. More pins will provide that surface area regardless of their size proportional to the tails. Increasing the number of pins will necessarily reduce the size of the tails, though.
You also have to consider what the joint is for. A dovetail joint is designed to be strong in a particular direction - resisting pulling apart against the wedge of the dovetails. It's not as strong when being pulled in the other direction, and the wedge shape of the tails and pins may even make it easier to collapse in the diagonal force direction that you applied. If you were to retest with a 90° pulling force instead of a 45° pushing force, your results would definitely change because the mechanical advantage of the dovetail would actually play a factor.
You remind me of when I pointed out to the one gentleman he tried to Say end grain to end grain glue up with stronger than long grain to long grain. But his test was flawed by the direction he was applying the force. As I explain to him if you were making a stool that was 1‘ x 2‘ you would put the grain running the 2 foot length. Now if you cut that stool and a half across the grain and just glued it up would you trust the stool to stand on? I wouldn’t now cut that stool instead of across the grain with the grain and then glue it back together now would you trust the stool? Yes I would. Which direction the grain runs is part of Woodworking that makes your end project strong if you do it right but weak if you do it wrong.
I say the same for the box joints, more glue surface more pulling strength
I would like to see the results of the pushing force.
I think dovetails that are more equally sized may contribute to extra strength as well.
Two women in a thread in a male dominated job subject, and being smart and relevant - my toxic masculinity is triggered and offended.. Keep it up ladies. ;)
Ordered as presented (breakage) in the video:
1. Butt Joint 60 lbs
2. Lamello 70 lbs
3. Domino 100 lbs
4a. Pocket Hole Inside 110 lbs
4b. Through Dowel Pins 110 lbs
4c. Dovetail 110 lbs
5. Pocket Hole Outside 170 lbs
6. Miter Joint 210 lbs
7. Box Joint 220 lbs
8. Miter with splines 270 lbs
omg ty so much
Strongest joint I've seen is also a type of miter joint. The lock miter joint, machined on the shaper, has outstanding strength due to the glue surface area.
I also couldn't help but wonder, would the tyloses in the white oak have made a difference by not allowing the glue to penetrate the pores?
I wonder how a pocket miter would do. I have often used those for small projects. Now that the miter and pocket were both pretty high on his list, what would combining them do?
I think the dovetail would have done a better job if it wasn't made so thin. My dad does wood work and his dovetail joints are much thicker than that.
Seriously, your dovetail was crafted by an expert. I'm sorry, the small contrasted with large dovetails is ignorant. The small dovetails will obviously break. Go back to structural engineering classes.
My theory on the dove tail is that the pins were just too small. Your box joint beats it just by having more glue area. I think you could get a significant boost with a 50 50 ratio of pin to tail
If you look closely the board actually split along the grain, spread, allowed the smaller ends to slide out
This.
It was a pretty bad example of a dovetail joint. I questioned it on first glance, and not surprise it failed spectacularly. The little details make a huge impact. Also you have to account of the same wood and same glue, which he didn't.
You can also cut dovetail joints in the trans-axis/dimension, which would decrease it's rigidity in the "pulling direction" but increase it in the "crushing direction". There's some interesting techniques in Ancient Japanese woodwork, and they occasionally used spines which really adds a lot of strength. That was no surprise to me.
Before the video here's how I expected it to go:
13- Butt Joint Glued
12- Lamello Attached
11- Domino Attached
10- Milter Joint
9- Dowel Pins Embedded
8- Pocket Hole Inside
7- Pocket Hole Outside
6- Butt Joint with nails
5- Butt Joint with screws
4- Milter with spines
3- Box Joint Proper
2- Dovetail proper
1- Dovetail 3D/spines
0 - Weld that sucker!
@@shadowanonymous3941 Dovetail joints present a lot of areas for stress concentrations. Stress concentrations in a linearly grained material can cause failures like this. I do agree that the small pin size may be a contributing failure factor, I would expect more equally sized pins/tails to be stronger in a situation like this.
Not so much the glue area, it simply slid . And with the angled cut it should have actually offered more surface area than a straight cut in a box joint. It most likely slid thru because of the angle of the cut and that was simply limited by the thickness of the pins (thinner material means you cannot increase your angle on both sides. The thicker box joint mainly offered a compression force distributed to both sides of each pin. The thin pins cannot simply be compressed on both sides to prevent it from sliding. That is, given that the pins have very tight fit. It could simply be that the dovetail pins were not as tight as the box joint. The fact that it slid instead of breaking at the shoulder means there is a problem with the fit. Of course, given the forces applied, the box joint will always defeat the dovetail in terms of preventing breaks at the shoulders since the grains are simply supported on all sides unlike the angles cut on a dovetail where the pins are smaller in diameter closer to the shoulder.
No, it's because dovetails are specifically strong against pulling pressure, not 45 degrees downward pressure. If it was a pull test, dovetails would be top.
As an engineer specifically in structures, the applied force and direction in relation to the joint have a huge impact on the results. The joint actually felt more force than the weight you put on top. This is called a moment arm between the joint and applied force. This is measured perpendicular from the joint and the applied force. I agree with you that more test would need performed as this is one case out of several cases and only measures the strength of these joints in a very specific instance. Still fun to watch and interesting.
Luckily, there's constants that can help determine just how much weight was applied on those joints as a result of the length of the lever.
And the test is valid for relative strength for the direction of stress it measured.
While true, the measurement of the force in pounds isn't really important here. What's more important is the comparative data - Having 5-10 of each joint would be helpful to take an average reading of the breaking-point of the joint. Also, instead of a levered arm with gym weights, using a hydraulic press with a more accurate digital readout would provide more accurate comparative readings. This is a good start, for sure.
Side topic from the video. Don’t have a degree in this field, but use moments, arm, and center of gravity (CG) all the time for work. If you would be willing to help us understand more. Wouldn’t you have to figure the moments being applied by finding the distance from the joint (arm) and then find the CG and multiplying them? You just used the term “moment arm” and I’ve always thought those as two separate things.
A better measure for the strength would be the torque in the joint. This depends on the force applied, the length of the lever and the angle between the direction of the force and the lever. Sometimes torque is also called moment which someone else here mentioned, so maybe we're talking about the same thing. Consider using torque to compare with new measurements or just keep the setup unchanged.
Great video and what a surprising result!
I would love to see this test done a second time with the same wood and joints, but this time testing the breakage in a pulling direction. As several already mentioned in the comments, different joints are strong in different aspects, and depending on what you're constructing you may need some joint over other.
In physics, we call these different loads *compression* (what was tested in the video) and *tension* (if we pulled the ends apart). We also have *torsion* (by twisting the joint) and *shear loads* (by dislocating one board out from the plane of the ∟-shape), that would be interesting to look at.
The differences in these strengths are actually quite important in fabrication.
For example, if we were to construct a box (with no top or bottom) using only Miter joints we would now expect this box to be super strong from what we just learnt. But this is not necessarily the case.. If we try to crush this box (by for example by standing on its edge), only two of the box's joints will be under compression (the two joints on the side). The other two joints (the top and bottom joints) will actually be under tension. So if the Miter joint happen to be very weak under tension, then the box will break pretty easy, even though the Miter joints are super strong in compression.
Wouldn't every joint here actually be tension and / or shear though? The inside corner of the joint in each case provides a fulcrum around which the joint fails. The box joint is basically just a bunch of glue joints failing in shear.
I was thinking the same thing. He could just take the joined boards and rest them on a level, low-friction surface in an inverted vee (^) shape, then apply a straight-down vertical force to the joint.
You'd also have to repeat the experiment many times and have other people replicate it several times to make it truly scientific.
@@monsterchimp1669 yes, science is very boring and hard work
@@crackedemerald4930 This was the first thing I thought of - 1 sample per joint is suggestive but not definitive, and it would have been a lot better to have a whole bunch of each joint. But he has limited amounts of time and funds. It'd be great, though, for a senior thesis in woodworking engineering, to have repeated tests. He could also have tested other types of joints (that I just listed in a comment of my own).
You defined my life as a woodworker: I like to make things stronger than necessary and more complicated than they need to be.
As a completely non-woodworker I definitely guessed the splines and was pleased my guess was correct. My thought process was that the way your contraption was setup is that it emphasizes compression on the inside of the joint which translates to tension on the outside of the joint. So I assumed those splines would be best to resist that tension since they are full grain wood running the exact direction of the tension.
You grasped the essence of joint engineering better than most woodworkers.
well, this will teach me to read comments before I finish watching the video!
Excellent analysis! This is the type of logical thinking I wish I'd see more of in woodworking. As Donny P said, most woodworkers seem to have very little understanding of these things.
im 16 never done woodworking in my life randomly watching this. And instantly knew the splines would win because the wood is going the same direction as the force. Like its hard to tear a pice of wood by pulling on it or i n this case compresing. idk
Exactly, had he tested the expansion of the joint under the opposite load instead, then the joint would have failed earlier.
An excellent video that triggered a storm of responses and professional opinions. Wow! IMO, your practical experiments taught us all a helluva lot ... grain, surface area, geometry, glue, the value of trial and error ... a thoughtful human effort. Thank you for your hard work!
Great test!! But the very first test, butt joint, and simple mitre. I worked in a custom mill shop most of my life and we found when gluing them, glue up the joint, put together and let it set for about 10-15 minutes without clamps etc. Then we released the pieces and added another layer of glue, then clamped it, WHAT A DIFFERENCE in strength!! Back when the moldings were applied to cabinet door and drawer fronts we never nailed anything, just glued with small hand clamps and with drawers and cabinets always slamming shut we NEVER had problems. DOUBLE GLUE!!
You all found a way to manage the increased absorption of glue into the capillaries that we all call grains. Well-done, sir.
Regardless of strength, I think contrasting splines in joinery is a great way to add character to what could be a simple piece.
Except you get to add character AND strength. I always enjoy form + function.
A lot of good suggestions in the comments. One thing I would add, it would be more beneficial to do multiple tests of each joint. It is entirely possible that one or more of the joints failed earlier than a typical example of that joint, and it is also possible that one or more were hero joints, holding on longer than a typical example of that joint. I know it is more work and cost to make and test multiples, but it would help to establish more reliable results.
I had this thought, too. He put so much effort into this, so I don’t want to seem flippant, and you don’t seem flippant to me, to be sure, but IMHO science would require multiple (at least 3) examples of each to test just because, like you say, any one of those joints could’ve been a lemon. This kind of research is absolutely awesome, though, and hats off to this guy for making it happen.
Agree. There's a video about glue strength that did 3 of each and sometimes there was pretty big sample to sample variance. Maybe he just got a bad dovetail :)
@@Bob.Silverstein I don't know if you remember this, but about 10 years ago, there was this meme floating around of a child's science experiment where she fed one plant tap water and the another plant water that had been heated in a microwave oven, then allowed to cool. The one watered with the microwave-heated-then-cooled water died while the other one flourished. So a lot of people started to avoid using the microwave!
Follow-up studies were significantly less viral, unfortunately, but they sampled a lot more plants and it turns out the kid just had a bad plant that wan't going to make it anyway - and it happened to be the one that got the microwave water.
So, anyway, I'm speaking to the choir here. It would triple the time and resources required for his experiment and if I was him, my eyes would be rolling, so I also want to emphasize - I really appreciate this video and the spirit in which it was produced.
@@sivacrom agree on the extra time taken being pretty steep. But perhaps it would be worth picking six of them: butt, miter, spline miter, box, dovetail, outside pocket screw. Another thing I didn't even think of is that it might differ for hardwood and softwood for a variety of reasons. Softwood might take glue better. Hardwood might support screws better. So one could get very different results with pine versus oak.
@@sivacrom also, I do remember experiments like the one you mentioned. Not surprising. You could even show that singing to a plant causes it to grow twice as fast, if you have an N of 1 :)
Miter had me stunned! Thank you for running the gauntlet! Also, stray option that might help:
Drill into the narrow edges of the box-joint, and plug with wooden dowel (imagine if you were making a 'hinge' out of wood, dowel plugging through each 'tooth' of the box-joint) to prevent the two boards from tilting out of alignment; it should force the inner dowel to fail, first, which'd be difficult in that confined bore.
I think the idea of the dovetail being so superior is that as it begins to come apart or loosen up (say in a really old drawer that’s been opened and shut A LOT) it still functions whereas a miter, box, or pocket hole are basically shot the moment they start to loosen up
Ummm... sand and glue it again?
@@lisat9707 not very easy for someone who isn't a carpenter or doesn't have access to a workshop.
Super good point. It still holds together-do’n its job- even though it’s injured.
I'd like to see a joint I have used a lot: a rabbet joint both glued and nailed as well as glued and screwed. Really enjoying this content.
I was really hoping he would do butt joints with brad nails, structural nails, and screws.
I would like to see a Greene & Greene style box joint tested, one with dowels and one with screws. It's probably not as strong as a conventional box joint but I would like to see how it holds up compared to the others.
Would be cool to see how miter-lock joints would hold! Incidentally, I make my bee boxes with splined miters and they hold up better outdoors in the sun than the traditional box joints that most use. I didn't know it would be stronger but less end grain exposed to the elements seems like a good idea.
The strength of the miter joint is really surprinsing. A few thoughts on that:
- Since your miter joint is 45 degree, and you placed it in a 45 degree angle, the strain is ideally angled, as the joint should "see" no to little shear stress. I wonder what happens, when you alter the force direction.
- The surface area is around 40% greater than that of a simple butt joint.
- The cutting surface is a mxiture of end grain and long grain. Could you do a test, where you presoak the endgrain in a mixture of water and glue, let it dry and then glue it?
Super interesting video! I feel like such videos really bring reliable knowledge to the community!
Its not so much the angle. Technically its an arm of momentum thing where the inner corner is the centerpoint.
Looking at that, it is important, that it is not only 40% more glue area, but the additional area is also at a larger distance to the center of rotation, giving it a much larger arm of momentum.
If you calculate effect, you'll find, that those 40% can hold the same weight, as the first 100%
So only from that effect, you could expect double weight.
Adding those splines improves even more especially at the longest arm.
Another interesting thing is, that this connection does not apply any stress onto the fibers, that separate them from each other (as happens in the butt joint) They are mainly and in a bunch pulled in their fiber direction.
Really would like to see how it would perform if the glue surfaces are prepared (pre glued).
You want sheer stress in a test like that. Lap shears can resist a lot of force. The main problem here is the glue being used or the bond line that is generated is insufficient.
@@wildeast66 I'm curious to see how things would change if a high strength epoxy was used instead.
@@MarkPryor1 Mee too.
Another interesting thing with the 45° miter is the taper of the wood to the point of greatest tension. This helps to minimize peak tension stresses. This turns out to be more effective than shear stress in the other style joints.
The dovetails we used when I was making furniture, were more like your box joins in size and spacing, just dovetail shaped. Maybe the size and number made a difference.
I think the big difference with this test is the amount of friction you can have versus tensile strength, maybe the ultimate joint would be the mitre with splines, but have the splines being evenly spaced and sized to the actual join wood, or at least increase the number of them. I have no idea really.
Its so funny that only you say it… we learned in school that it have to be in a specified ratio, so the gap cant be thin like in the video. Its look good but not as strong.
I don't understand the point of those dovetails where tails are thick and pins are thin.
tails and pins should be about the same thickness as the thickness of the board or slightly wider.
I'm not sure if it's done that way for esthetic reasons, but they don't look nice to my eyes.
Yeah, the thinnest part of the dovetails become the weakest link. Bigger splines don't do anything, they just add surface so more thin ones would be best, but not too many to make the wood in between them too thin.
I was surprised that he didn't include the typical routed dovetail joint that is the industry standard in cabinetmaking.
agree. Seems the dovetail was too thin and we can see on the video that it was the timber that failed (because it was too thin) and not the joint or glue.
If you are still doing this.. try angling the outside splines in your mitre joint instead of all of them being parallel with your downward force. It could be as little as 10 degrees. Also, try some angled dowels as splines toward the inside of the joint. My theory is that the angles will transfer some of the downward force into other directions (namely into the wood itself) which would weaken the overall downward force applied to the joint. I also believe that there is an optimal degree of angle for maximum strength. Too high would be much less effective and would probably weaken the joint.
Also would be interesting to see how much the material used for the splines/dowels matters.
It‘s likely that in softer/weaker woods, dowels and splines made of strong woods would have a greater impact on joint strength.
I recently saw a gizmo for drilling dowels at opposite 45 degree angles (I think on 731 woodworks‘ channel?) which locks the joint together. Thought that was interesting. I‘ve seen many finish carpenters take that approach with moulding and brad nails, angling them opposite to lock it in, but hadn‘t seen it previously with dowels.
Longer dowels too.
Great suggestion
That was really cool. Now that I’ve seen it I can see several variables to consider. For the dovetail and box joints the strength would be affected by how tight the joints are. William Ng has talked about this in some of his videos. For wood glue to perform at its optimum strength it can’t be too tight or too loose of a joint. For the tenon, dowel, and spline joints the walnut splines likely we’re stronger than the dowels and tenons assuming those were just pine. And for any joints using end grain my high school shop teacher taught me a trick to make them stronger. I was building my Mom a bookcase out of hickory and due to time constraints I didn’t have time for fancy joinery to attach the top so it is just a butt joint where the top sits on top of the sides. He had me thin the wood glue with water and apply that to the end grain a couple of times and let it soak in without assembling the top, then after it was dry I came back with just glue and put it together and clamped over night. That was in 1975 and it has never failed in spite of being moved many times by lifting it by the top while fully loaded with books.
Dear Wendel, thanks for doing this test. It certainly revealed some surprises, particularly the dovetail joints. I built a bedroom suite 40+ years ago using veneered chipboard for the walls of the furniture modules. The only joint I could make easily was a mitre joint with glue. Despite decades of abuse, no sign of breakdown. I got it right way back then before your video {or computers or internet etc}. Cheers.
Loved watching thee tests and the method you used. The dovetail could have been starved of glue. To many people make an ultra tight joint. No room for adhesive. I spent a good part of my life as a Cabinetmaker. And made hundreds of dovetail drawers via a dovetail jig I made in the shop. I found that I needed a certain amount of slop so that there could be proper glue joint allowance. Too tight and I squeezed out all of the glue.
I imagine the same is true for box joints
@@tomruth9487 Exactly.
It very much looked like it broke on the glue edges (which are long grain to long grain) - I think you're right.
As a structural engineer that designs wood connections all the time, it would be really interesting to test the strength of something other than the glue. Some of those connections seemed quite strong if it weren’t for the “snap” of the glue bond failure. I’d love to see just how high you can go with things like truss plates, angles, and structural nails and screws. Obviously a carpenter isn’t making a cabinet to withstand an earthquake, but I think it would be fun either way.
All my cabinets and shelves seem to have withstood multiple earthquakes. Perhaps not good for their structural integrity but nothing has fallen apart,not even the antiques.
As interesting as that may be, I think it would get really silly really fast. Heck even this test showed that steel vs glue is no comparison. The pocket holes had 2 screws and it put them in 4th place even though there wasn't a lot of wood to hold them. Something like a truss plate, you instantly get to the point where you pretty much just find the weak spots in the wood. Which if you think about it makes sense. Its kinda why we invented truss plates lol. The only reason miter was so high was the leverage gain of having that glued plane being level.
Yup. That's why I just use glue, maybe pin joints if it's a bookshelf but most modern glues can handle what I can throw at it. Worst comes to worse yoy can always add support.
Need too much weight. You would be looking at thousands of pounds unless you are using quarter inch stock.
Sounds like you have a plan for a UA-cam video in the making
I would love to see the follow up video to this with more tests:
• different sizes of dovetails/fingers
• different wood glue uses
• different woods and whether or not cross-hatching helps wood glue hold it tighter
I liked and subbed!
Its pretty rare that a drawer or box is stressed that way. I would love to see these tests repeated as a pull test instead (think the pulling action on a drawer).
Yes please! Although I suspect that the miter with splines may still come out surprisingly well.
I also wonder how much difference it would make if dowels and/or loose tenons (dominos) were perpendicular to the force applied to parallel to it. IOW which end of the box angle you pull on probably makes a difference.
Another interesting test would be sheering force. Make a T like a shelf attached to the side of a cabinet. Apply downward force close to the joint. How do pocket holes, dominos and dowels compare to a dado & rabbet? (Hint: I’m pretty sure I know the answer.)
Scott Walsh did a video with pulling for the test with opposite results. The miter with splines was the best and box was the weakest.
I'd like to see the test after the pieces have aged for a year or two. I suspect the miter would turn out to be one of the weakest joints. What we're seeing is the strength of fresh glue here, not of the joint.
Miter joint also significantly changes the angle at which the forces are transferred between the two boards. That could have an impact here. It's plausible that if forces were applied at different angles the miter joint would turn out not that great.
As a full time engineer and hobbyist wood worker this is a fantastic video. I will say that by applying the weight to a lever arm you're testing the torque on the joint rather than the weight that it can hold. But because each test piece is consistent you do get reliable results and eliminate quite a few variables. Great to see you invested in a lab coat as well for science!
Great comment! Lol. Lab coat! Most "Doctors " are the same. They just google what pills to give you for the symptoms NOT the actual cause. But that is for a different discussion. 😜😊
Yes, it's actually the law about force and lever action that applies.
The cross-product of force and distance is torque. So what we needed in this experiment was the distance from the end of the board to the center of the joint thus calculating the actual force applied to that joint. The result would be a figure in Newton meter or Nm, not in pounds or kilogram.
However, I think we should leave all the complications out of this equation and see it as a practical experiment or proof of concept. ;)
Yeah nah I wouldn't say it's torque. Because if you put the same weight further out from the pivot point it would still put the same force acting down on the joint.
Or are you talking about the wood joint being the fulcrum? In any case, as you say, the experiment is consistent. It's comparing different joints under the same test conditions, and using the amount of weight on top as the variable.
@@JebediahKerb it entirely is torque. this is a textbook example of a 2D moment of force. statics 101.
@@Pan_Galactic_Gargle_Blaster it would only be torque if it was driven from a motor at the axis, or if a constant weight was at a constant distance and the force on the joint was at a different distance. Then you would talk about torque. But the weight is directly above the joint. It's always going to be the same amount of weight on the join if you have the weight directly above it, no matter how long the arm is. You could measure torque on the hinge, and that would change based on the arm, but the weight on the join is always going to be the amount of weight you put above it. He even showed this in the video.
Testing under a tensile load and testing fatigue strength to cyclical loading would probably have very different results and would be interesting to see
Thank you for doing this. I have some ideas for a project that specifically requires me to know what wood joints would be best. You saved me a lot of time
An interesting thing is that the splines can be added to a miter joint after the fact.
One part of the strength of the miter is that it is end grain to end grain, and wood glue generally works best that way - as it seeps into the pores, it effectively makes tons of tiny glue dowels in every pore of the wood.
Nice
A point on dovetails, I've notice from looking at my late Grandma's 100 yr old furniture. Dovetails are everywhere, but there is zero glue. Seems to me that dovetails were not developed to be a strong joint that stands up to compression force, but to stay together along a specific direction of force before glue was a thing that saved all mediocre wood workers (
tension strength of most wood is insane. straight grain fir is like a million pounds per sq inch. try pulling a toothpick apart.
@@victorhopper6774 You are correct, but tension strength of the joints is not the same as the wood.
Yes that is why dovetails are used a lot in drawers.
There was definitely wood glue 100yr ago. Humans have been using glue for 70,000 years. Egyptians used glue for wood furniture 4,000 years ago.
Your grandma just bought some junk, either missed the glue or used something low quality that deteriorated. Dovetails are definitely traditionally glued.
Yes glue made from bones for example
mechanical engineer: my take is that the way dovetails are hand cut left a stress concentration at the inner edge of the tail (see failure pic for where it split). this is where the saw stops when hand cutting the tails. routing the dovetail would likely do a little better job (similar to box joint). altho box joint would still be better since it is shearing the glue only and not exerting a force that is splitting the tails
One thing I'd add that I haven't seen mentioned yet: testing for max strength doesn't necessarily account for the effect that cyclic loading will have on a test joint - the goal with a drawer isn't to withstand a single incredibly forceful push/pull, it's to withstand pushes and pulls over the lifetime of the piece, as the materials age and as the piece undergoes varying environmental conditions.
That's not to take anything away from this testing methodology. But rather, to point out that this test isn't going to give someone all the information they might need to select a joint design for a project. More specifically, I don't think it's reasonable to conclude from this test alone that dovetails are mostly for aesthetics.
Beyond that, other people already mentioned the difference between static and dynamic loading, and I would emphasize that: it would be good to control for _how_ you apply the weight, to make sure that you're not (for instance) dropping the weight more when you're worried about a high stack of weights toppling onto your foot.
Someone else has mentioned using a forcing screw, and I know Matthias Wandel already uses one for his experiments. Something like that would be a much more repeatable way to load the joint.
I've found that while butt joints offer more than enough strength in a single instance, the repeated strain of opening and closing the drawer tended to cause failure over time... but this was still a valuable and interesting video, thanks as always for posting!
Indeed, impact strength is not the same as tensile strength!
Pocket screws seem to do that over time also.
I knew the miter joint would be in the top 3 because it increases the surface area by the greatest amount AND in the same direction, i.e. in line with the grain. In 3/4" wood it's about 1" high by whatever the width of the wood is. I use this for building speaker cabinets, and I was originally surprised at how strong it is - especially when it's a box and not just two boards. The dovetail and box joints actually reduce the effective surface area quite a bit; in the context of this test, the sides of the fingers provide little to no structural integrity because the force would be torquing on them rather than pushing or pulling.
I'd like to see a mortise and wedged through-tenon setup (not dominoes) for the next go around. I suspect it would out-perform the dominoes and dowels, but it would be interesting to see the results. With that joint, the wood should break before the joint, if done correctly. That's been my experience with them anyway.
Also, how do you NOT have a dovetail jig in that shop? Seriously. You literally have all this stuff nobody has ever heard of, but you have to outsource a dovetail? That alone may have blown my mind more than the test results.
Anyway, really enjoyed this. Looking forward to round 2!!
A corner joint such as being tested here, is not the correct application for a through mortise and tenon. It would not be strong at all. The end grain of the one piece of wood would just blow out.
As far as I can tell, the boxjoint (fingerjoint) was stronger than the dovetails, cause they were too delecate and thinn. If you’d made them more even in width or made more dovetails (5/4 or more instead of 4/3), like on the boxjoint it would have held more lbs.
Would have been interesting to see the box joint compared to one with more, narrower fingers, and even more glue surface area!
Dovetail is a fundamentally flawed joint type. Reguardless of the size or amount of em. All the pressure from the weight ends up on that small short "triangle" shape at the sides of each dovetail. So just as you saw, the wood will break on that triangle line leaving one side looking as if it was a box joint because that small wood section ends up as the weakest part of it making it much weaker than a normal box joint.
Thank you very much for these tests! 👍👍👍
If it can help francophone to have an overview of the results :
- Joint basique (de bout) : 27 kg
- Joint lamello : 32 kg
- Joint domino : 45 kg
- Joint avec vis noyées en biais (type Kreg) placées à l'intérieur : 50 kg
- Joint avec tourillons : 50 kg
- Joints avec assemblage à queue d'arronde : 50 kg
- Joint avec vis noyées en biais (type Kreg) placées à l'extérieur : 77 kg
- Joint à simple coupe d'onglet 45° : 95 kg (!)
- Joint à queue droite : 100 kg
- Joint à clés d'angle : 120 kg
The dovetail wedge shape splits the wood in half due to the loading, that's why it's weaker than the box joint. It's strong in tension, not rotational loading
The thickness of the top of the pins and the angle of the dovetails matter alot as well. I always make my dovetails with half an inch at the tap of the pins if structure matters at all.
I'd like to see a dovetail angle shootout one of these days.
The thin pins is what had the dovetail fail .. someone should recreate this test with a dovetail /pin 1:1 size ratio ..those thin pins looked nice but didn't provide strength .
The glue surface area is part of it, you're getting (I think) 1.4x the surface area.
There's also the question of leverage. The inner corner of the joint is the fulcrum, with the board is one side of the lever and the outside corner is the other side of the lever. By using the 45 degree cut, the short lever (the joint) is lengthened by 1.4x.
I was surprised it made that much of a difference, though.
This comment should have more likes
Agreed, this is the way I would flex the joint to break it but also not how mitered joints on a drawer are used so I'm not sure the examples are applicable to the the intended end use they were designed for. Also all joints were glued and some designs were developed to be used without glue at all. I'd like to see that basic mitre joint hold up to its own weight even without glue! The other problem with using glue is that this just becomes a test of which joint has the most surface area along the long grain of the wood. And for that it could have been simply mathematically calculated without even testing and probably predicted fairly close results to this.
The miter joint is surprisingly strong in this direction for both of the reasons you listed, and two additional ones:
1) It's actually more like an edge-grain bond than you'd expect. And edge grain bonds are all about surface area.
2) Wood glue is stronger than many woods IN TENSION, not in shear - this is why the miter out performed the box joint - it's all about how much glue you can get in tension when you load the joint up.
Rad 2? He's a witch!
Mathematically the leverage effect amplifies the whole thing to hold factor 2 instead of 1.4. so there must be something more.
And I guess that is the direction of load on the fibers.
A butt joint with that "leverage" load, actually pulls the fibers of the long grain wood apart from each other. In that direction the wood is very weak.
If the force had a direction parallel to the fibers (which would be typical for that type of joint) they would have hold much much more.
For that specific load shown here (which you try to avoid in ANY construction by creating triangles) the miter joint loads all fibers in their strongest direction, which gives the additional strength compared to others.
That is, why the test is on one hand very interesting indeed, but of limited help to woodworking, as the direction of the force is very important. Even a butt joint has two different strengths depending on the direction you load them (parallel or perpendicular to the glue surface)
this video rocks. the comprehensive study of basic woodworking joints is really useful for woodworkers of all skill levels. miter joint... wow.
it'd be interesting to do a test on joints 1 year after they're glued, to see what kind of effect time has on the glue/joint integrity.
Glued? My joints get me only hammered. Where's the glue coming from?
Time is one thing, I would be more interested in repeated loading. I doubt that box joint would hold up well if you put 30 pounds on it 100 times.
Ya, hopefully people don't start making drawers with miters because of this, lol. While this video was cool, the test was more or less irrelevant. The vector of the force was different than a push/pull force a drawer would receive. For a miter join, the glue would take all that repeated force over years which would inevitably lead to a failure. The dovetail, however, is distributing that force to wood-on-wood contact. Meaning, for the joint to fail the wood itself *must* break. You don't even need glue for a solid dovetail join. Fun test, fun video, but ultimately "wrong" and misleading.
@@JustinSmith1287 I don't see the miter joint failing at all on a drawer if you add splines. The joint is so simple it shouldn't work so good, but apparently it does.
@@sh0cktim3 I dont see it failing anyway since decent wood glue is stronger than the wood its holding together.
One more consideration is the impact of the joint ‘failure’. Some of these options fail catastrophically, others (particularly the pocket screws) would hang on as a kind of hinge.
Also the ease of repair though. If a glue but joint fails, you can often just reglue it and you‘re good to go (after sanding off the remaining glue, provided it broke on the glue joint and didn‘t destroy the wood too much). With failing pocket screws, it can really tear up the wood.
I always found that applying a layer of glue on end grain and allowing it to dry to tacky then apply a second layer and affixing the joint it results in a much stronger bond. The initial layer will absorb into the end grain and the second layer will bond to the first and both boards. You then have a very deep glue bond to the end grain board.
It would also be interesting to do the same round of tests using two part epoxy resin and see the performance difference compared to wood glue.
While I know it’s generally not feasible to use epoxy for most wood projects nor is it necessary to have that much strength, I think the results would be surprising.
I used to make custom knives and used Smooth On epoxy for handle retention with dowel pins as the mechanical connection. Since most of the knives I made were bushcraft knives and would be put under serious use, from chopping and batonning and occasionally throwing, the handles needed to withstand enormous amounts of shock force.
Wendel did these tests a decade ago and determined with some confidence that the only thing that matters is total joint surface area with glue. The strongest joint will be a box joint with many, many cuts to produce a lot of surface area.
A tight fitting box joint with skinny fingers, lol.
@@collina.7336 giggity
How about a mitered finger joint.
Given the options for different spline counts and orientations, ie. angled, a follow-up video is required. All hail the splined miter!
Others on youtube have run this experiment, applying pressure a little differently and come to the exact same conclusion. It's fascinating.
Awesome test and wonderful neutrality. I guessed it right! I figured the splines would essentially act as struts for a triangulated joint.
Right, my pick a stronger joint would be: Box, with a dowel run longitudinally through the assembled joint. So visually it looks like a hinge pin. Just need a long drill bit! (I just made that joint up in my head.)
Great video, very interesting. I'm a retired carpenter and I briefly studied Japanese joinery about 40 years ago. They use incredibly intricate joinery that has to withstand earthquakes. I was buying Japanese shark tooth pull saws years before they became popular here in North America. We had one time use feather files for sharpening them. They also use slip joints so that during an earthquake the joints don't snap and break they move around.
Unbelieveable! Virtually every drawer in my shop is made with box joints. 1000's of cuts. I am going to switch to the splined miter for all my future drawers. I need about 50 in the kitchen remodel I am doing and this will save me HOURS of time. Great test.
Great video! For some reason I suspected mitre joints to be rather strong, not simply because they have more surface area to hold glue, but because they convert the pressure on the joint to compressive force entirely eliminating torsional and shearing forces where the glue can best resist. but I never guessed they'd be THAT strong. There's one joint I presently go to more than any other; it's a locking mitre. For solid wood, I just use the router bit. For veneered plywood, I use the table saw, dividing the thickness into thirds, use the inside two thirds to create a locking dado, leaving the last third mitred. (Obviously, this is easiest using 3/4-in plywood.) It hides the plywood core completely leaving a finished corner inside and out, and I can orient the joint to oppose the direction of greater stress, and so far, they seem to hold an incredible amount of weight. I'd be excited now to see how well these test. Thank-you for this video.
I would think a locking mitre would win, and I was disappointed that it was not included in the test..
Otherwise it was an excellent video.
Great video!!! When you redo the video, use Titebond III, it supposedly has a higher strength rating. Also TB1 & TB2 both tend to be far more brittle when fully cured, while TBIII can flex when cured which means it 'should' hold better & longer.
As soon as I saw the thin pins on the dovetail, I immediately thought that it would not perform well. Looked to me like the dovetail board cracked then just separated, though honestly, I expected those thin pins to break off instead.
Credit where it's due - these videos are both informative and amusing - and also nicely put together - Good Work Sir! Good Work
I agree with many of the other comments. As an engineer, I would like to suggest you an interesting upgrade for the test bench. Usually those tests are considered almost static while adding many pounds with weights isn't. I would add a screw to push the test piece: doing it slowly will make the results more precise (also more than one test is better, for engineering results we do 15 tests).
I was thinking of adding water, but a screw is an interesting idea.
I was wondering if we were going to ignore the shock loading factor of dropping those weights on. ✌
@@aslacker That would be an interesting separate set of tests.
Enter Mathias wandel
Funny how you dont comment on making 5-10 of each joint to rule out defects in the wood and produce some statistics. Also, standardizing the assembly procedure more to eliminate as many variables as possible would also help. Also, thirsty endgrain glue-up was the strongest joint, even though he kept saying it would be the weakest throughout the entire video. In my experience, end grain to end grain is the strongest when the glue is done like this: 1. Add glue. 2. Wait 5 or so minutes and add more glue. 3. Squeeze the joint together.
I love videos like this. Yeah there were a few things that could have been done better as mentioned in other comments, but in general, I learned something new. And that knowledge will come in handy when I go to do my own projects. Thank you for the informative video.
The first time I saw the beginning of a woodworking video was a gym activity. out of the box
My ideas for a strong joints:
-The 45° angle with thicker splines (similar to a box joint). Reason: It appeared as if the splines were actually the weak point.
-Box joint but with a pin going through all of the pieces. The weak point of the box joint seemed to be the glue. So a pin should increase the strength by taking some of the load away. Another option would be to make the boxes narrower so the glued surface increases. That would of course combine well with the pin. If you want to be really fancy, you could try to reinforce that even more with some pocket hole screws. I think the possible strength of this is really just limited by the strength of the wood itself.
-The spline thing but with deeper cuts so the splines actually go into the inside a bit. Another fancy way of doing this eould be to have bent splines so you are not dealing with pulling the grains apart.
I was buying wood at an Amish place once and they mentioned that mitered cuts almost acted like edge grain to edge grain. I was still surprised to see your results and still feel like a miter needs a spline.
I made a diploma frame for my son and did miter with splines. I wasn't sure if the splines would add much, but they looked pretty and I wanted to learn how to do it. Glad to know it might actually survive the inevitable dropping off the wall. I mean, he hung it right at the edge of his VR space. Thanks for opening up this Pandora's box of joinery.
I wonder what kind of joints Pandora's box has.
Redo the dovetail. I'll explain. Yes it's the pin size to tail size. That style of dovetail is made for strength in pulling a drawer. Equal pin/tail sizes will be much stronger for the test you ran.
Edit: also, increase the angle of slope to about 9° or 10° and make them half blind. You'll be suprised at where they end up. Probably top spot.
Nice vid. Very informative.
I have a router bit for locking mitres I'd be interested in seeing tested. I suspect the locking mechanism is just to help alignment rather than strength, but it may increase the gluing surface by a percentage.
After seeing a previous comment about locked miters, I had to google the term to see what it meant. The first hit was for a router bit like you mention. It showed the resulting joint geometry, which led me to the same conclusions you mention: more alignment than strength, perhaps more gluing area, but not likely to add much strength as that geometry would just pull apart under the stress of this test [minimal extra strength at 2 or 3 very small points in the "key"], mostly subject to the additional glue strength.
That was a great experiment. I have to admit that I had the miter joint not lasting much longer than the butt joint, which I di have as the weakest. I also thought the dovetail with all of it's glue surface, and the cuts at angles would be stringer than the box joint. You learn something new everyday. Thanks for doing this!!
Great vid, Jason! If you do end up repeating this, I'd be real curious to see a lock miter joint included, especially since the mitered joint was so strong. Cheers!
Yes for lock miter joint inclusion.
Great video. I almost had the order right. The mitre surprised me for sure. I make cabinets everyday and only use box joints. Making sure to get a lot of glue on all surfaces...most will het squeezed out as you know on those tight fingers.
I think the angle that the weight is applied to each joint could have an effect on the outcome. Hence the mitre would maybe be stronger or weaker depending on the direction the weight is pushing on the joint.
Anyway thanks for the great video, I always wondered about different joints.
I'd like to see a test for the opposite direction of pressure. Clamping boards to something upright and placing the weight on the outer edge to test joint integrity. I think a few of them would fare better and a few worse.
The other great thing, you’re never going to be putting that kind of pressure on those joints at that kind of angle. But all around super surprising. I thought the miter would be SO much weaker!
This was great, thanks for doing it! After Patrick Sullivan's recent videos on glue strength (and the VERY surprising result for end grain) I was expecting the mitre to do far better than most would expect. And their good showing is a testament to how accurately you cut the joint, and how well you clamped, so extra kudos there. I was surprised about the plain butt joint, I thought that would do better than last place (even if the result does show it's not actually too weak to use); I honestly expected the Lamello to do slightly worse, because of the smaller glue surface area.
Nerdy nitpick 🤓 the reinforcement in the winning joint, those aren't splines, they're keys. Splines run _along_ a joint, keys cross the joint (just like in butterfly keys).
And yes yes yes, please do some follow-on tests 👍👍👍
the Sullivan video is really eye opening and had a lot of professionals irritated.
Same here! Patrick's video had me putting miter joint way up near the top, but I didn't expect it to be even stronger than the box joint.
@@tchevrier Yeah that's a great way of putting it 👍Did you catch how some sort hinted they already knew, or more directly stated that, "but......" But what? If you'd believed this before you'd already have content about it 😆
I bet it wouldn't be hard to go back through vids of many of the big names that responded and find direct proof they *didn't* think this was the case, stuff along the lines of
_"I don't bother to put any glue on the end grain_ [in a dovetail] _because it adds no strength"_
_"90° butt joints need to be reinforced [because, end grain]"_
etc.
I am pretty sure I've heard Cosman saying something related (although I haven't watched him in years so very vague memory), and maybe also Marc S., Sellers, Stumpy, Ramsay *and* Broun!
Biscuits are splines. I have had astonishing luck with those for 30 years.
In wood aircraft construction, where the least wood / lightest weight, and greatest strength, are essential, joints are made by using glued internal corner blocks and exterior glued thin plywood plates that cover the joint. Nailed together. This gives tremendous resistance to the rotational force that you are applying.
Thank you so much, Bourbon Moth Woodworking.
The fact that the box and dovetail joints failed so perfectly at the glue points makes me think maybe they could withstand more with a better gluing job. My joints almost always fail at the wood and not the glue.
Definitely looked like inconsistent glue to me as well
Funny thing about that. Wood glue is usually stonger than the "natural glue" the wood has to keep the fibres / grains in piece - the lignin. So a piece of wood is more likely to break along the grain than in the glue joint if the glue job is done right with good glue. That being said end grain glue joints should be stronger than side grain glue joints (cause the wood wont break across the grain before the glue does), given the glue is applied well enough!
Epoxy is superior to wood glue. This test shows in a few of these examples that the wood glue used is less strong than the wood itself.
I agree using a superior and more consistent adhesive would make the test more interesting.
It wasn't the glue difference but the surface area difference. More dovetails evenly spaced or a finger joint would also increase the strength
literally thank you so much. i was able to use the info in this video for my physics project
If you continue your science experiments I would love to see a comparison of smooth dowels, fluted dowels, spiral dowels, etc. I feel like there's probably minimal difference between them but it would be cool to see actual testing performed.
I agree. Having used Lamello joints using the wood bisquits i have found them stronger than dowels or splines (depending on wood types).
The original Lamello joint is using angle grain compressed beechwood. Like the biscuits made by Lamello.
In one of my past lives I managed a mechanical test lab so this experiment was really exciting to watch. My only observation is that of your comment about the miter joint. Yes clearly, and surprisingly, it appears to be a very strong joint, but the unit of measure that you are really after is Torque which is load (weight) x Distance. The further away you place the load, the more torque you will have and therefore the total load that you will be able to place will be lower. But thus far, yours is the best video I have seen, good job!
I'm absolutely amazed by the miter joint! I've made a billion miter joint things and even had some break when dropped on the ground so . . . Just seems crazy.
Next time with your dovetail don’t make your tail so small. I know it’s part of the classical look of a dovetail whose primary design is to keep the wood from pulling apart after the glue fails. A lot of people don’t realize that the older glues sort of had a lifetime and then the joints would get loose and have to be re-glued together. Your Old hot glue’s just didn’t have the life expectancy of modern glues. Anyway with your next dovetail Make your tails and pins closer to the the same size so that it’s spaced closer to the spacing of the Box joint. I also noticed you didn’t do a proper through mortise or a mortise in a rabbit. I’m thinking the strongest version of a mortise and tenon joint you would start by cutting a rabbit at the end of one board and then notch out across that rabbit so you have protruding fingers like a box joint then in the other board cut matching square holes to be the mortises of your tenants. Your tenants would be about half the thickness of the board and depending on how many you make could be how about any width you want. And down for what I believe would be the strongest joint make a box joint but then drill a hole through all of the individual fingers top to bottom and put a thin hardwood dowel interlocking the fingers of your box joint. When it’s all done when you look at it from the sides it will look like a normal box joint but when you look at it from the top or bottom you will see the dowel down in the end of the board as a little circle.
I was thinking the same thing about the dovetails. Equal sized pins and tails and a more of them. That'll increase the glue surface.
@@johngray2875 And let’s not forget making those small itty-bitty pins is a weakness unto itself. Anyone can pretty much breaker matchstick it’s a lot harder to break a three-quarter inch board.
Yup, and conversely, making a modified box joint where the tails on one side are 1/8" thick would probably behave similarly to the (lovely) thin tail dovetailed board.
Dovetails are designed to be mechanically strong, in the direction of the joint. You applied a force in a direction that is 45 deg of the axis so the joint is less effective. Although, I can't be sure but I think the glue up needs to be more careful. The mortise and tenon is definitely one of the top strength joint, the Domino was not a good example, they were too small. I love my Domino machine so it's not a knock on the tool. I want to let you know how I appreciate you doing this.
Please forgive me, but your your "tenants" are tenons - for a mortise and tenon joint.
So the miter joint with splines actually is quite aesthetic, especially with contrasting-colored splines. And given that it proves to be the strongest, woodsmiths should consider these to be a worthy alternative to box joints and dovetail joints.
It really depends on the application. Almost no project is going to be subject to the same type/direction of force in this video. If you're making drawers, the dovetail is going to be stronger, given the direction of the force you will be applying to it, than even the splined miter. If you're making a box that you will pick up often, with weight in it, the box and dovetail joints will be stronger as well.
Perfectionism - starting from the beard - entangle every piece of workshop and work. As well as jokes. Admiring 🙏
I'd love to see this test done in the sheer/torsion direction - 90 degrees from how you had it. And see how the joints stack up there. Some might be better in that orientation.
That was extremely educational. I make mother joints all the time. I mostly put through dowels across the miter. That would be one to try. Oh and I use 1/4” dowels. I think that would be a good one for your next test. Great video as always
I love a good mother joint.
@@sirbrewzalot 😆
🤯 Wow! Absolutely insane! I was not expecting this result whatsoever. I love pocket holes and dowels. I thought a simple miter would have been the weakest. Thank you for taking the time to show us all of this. I've seen the splines before and just thought it was esthetics only. Now that I have a table saw, I really want to do splines. They are so pretty and now I've learned are strong too. I also learned that outside pocket holes are stronger. Did not know that. I thought they would have been the same result. Love your channel. Keep up the great work.
biscuit jointer works great too
This is also a test of the glue, all joints have an increased glue surface over the previous one. Excluding the dovetail, even though the joint was well executed the ratio was a bit off for this test. Spacing the dovetails more like the box joint would have helped increasing its odds.
There are so many different joints because they all serve different purposes.
This. The dove tail needed at least as many tongs as the box joint to be compared like this.
The last sentence is the most important. Joints are meant to be strong at specific direction(s) and also handle twists, not just wait, and also to look nice.
Every single joint caused the glue to fail. His glue is the weak point in every single joint. He needs to try this with better glue to compare the difference in strength caused specifically by the joint.
@@caleb186 yeah but if thats the glue he uses regularly then it gives him an idea as to the items he builds. Plus many wood workers use titebond II
I’ve always been lead to believe glue works best when cured under pressure. It would be interesting to see, glue under pressure vs. not.
Dale Zimmerman of Franklin International, maker of Titebond woodworking glues, recommends 100 to 150 pounds per square inch (psi) for clamping softwoods and 175-250 psi for hardwoods.
I'm looking forward to the follow-up video!
Also, I think the dovetail joint would have outmatched the finger joint if there were the same number of dovetails as there were fingers on the finger joint, and if the pins and tails were of similar size, instead of tiny pins and huge tails.
I'm a beginner and I was deciding what kind of joint I wanted to start practicing and this was helpful. For me and my equipment, it's the box joint. Now I'm going to watch your video on box joint and get ready to make my first box. It will be a Box Joint box. Maybe I make a smaller Box Joint Joint Box after that. With box hinges so it will be a box hinged, Box Joint Joint Box.
Also, throwing a rabbet joint into the mix might be informative, too!
Quite an imaginative testing routine! I wonder how a more traditional "finger joint" might fare. Also I wonder at the lever action of pressing down on that 90 D joint. I dunno, but am not sure that most such joints are subjected to that sort of vectored and leveraged force. Might it be a more indicative test, to possibly subject the joints to lateral pulls - or possibly constructing a complete box using the same joint at all 4 locations, and then putting the pressure to the entire box with your inventive rig? Still and all, you've gotten my mind reconsidering what I thought I knew about the construction of various wood joints and joinery, which is what I think you intended in the first place. Many thanks!
Very useful thank you. I also read another comment that the resistance depends on the angle at which the pressure is received, that also makes sense. Greetings.
Kinda had a feeling that splines would win, simply for the fact of long grain glue up and that the breaking would have to cause the spline material either to overcome that long grain to long grain glue bond or it would have to rip apart which is in itself pretty hard to make happen for wood. Imagine if you would eliminate the weak point of this joint by adding more splines and make them a little thicker, that would have to make the glue joint come apart, which would be exciting to see the weight of having that to happen.
I thought the miter with splines would be 2nd or 3rd place. Surprised to see it at #1.
I was also thinking about dovetail splines. I imagine those would be strong for several reasons -- glue surface, mechanical strength, grain direction, etc.
Isn’t that actually a keyed miter joint? Would love to see a miter with an internal cross-grained spline. This was fantastic.
my grandfather always used miter with splines and I've always tended to use it as well. It's easy to do, looks great, and with contrasting wood, really shows off the joint. would have been happy if it only placed in the top 3 or 4... nice to see it show up at the strongest of the group. :)
I think the dovetails failed because they were not even
Some of the tails were skinny and others fat. When you retest how about making them even like most people do. I love your videos and have learned so much. Thanks!!
Not at all surprised that miter with splines was first place, and it was my guess for first.
I knew plain miter was going to outperform most people's expectations too, but still had it halfway down my list. Of course for that joint glue technique makes a huge difference, since you've got to make sure you use enough despite the end grain wicking it away. (I always apply, let sit for a moment, and apply again after it disappears.)
Also miter with splines is my favorite aesthetically anyway. :D
I agree on the last point. It's one of the best looking. And I too thought he would have let the first layer of glue dry in the simple miter joint first, then add another bit of glue. Surprised he didn't do that.
Thx, you just made me feel a lot better about my short cut miter to make a support box for a small table top. I thought “oh it’s not very good but it’s only a 10x14 table 14 in high for my bathroom”.
I would be interested in what the results would be if you went with a dovetail mitre joint with spline and with the screws. Wonder if this combo could break the 500 lb mark.
Very interesting! I am a civil engineer and I would like to give a bit of info on the miter joint. Essentially, the force you are putting on, is put on the closest to orthogonal (the direction is closest to perpendicular) to the glued surface of all joints. With glue being best at pulling perpendicular to a surface, rather than having the shearing force of a less perpendicular joint, this is a great combination. Then lastly the miter joint has a greater gluing surface, allowing for an even higher pulling resistance. Its simple physics if you think about it, but it's not too obvious. In this test you basically only tested one direction of force. It might be interesting to test pulling force too, or a different pushing direction, I am almost certain the results will be quite different. With the right direction of force, the butt joint might even beat the miter joint.
I also heard a convincing argument that end grain is a BETTER gluing surface, provided it gets enough glue. Since the glue bond is stronger than the wood itself, the breakage of the wood is the real issue, and wood splits a lot easier than it breaks. Therefore, my theory is that the miter is stronger because it eliminates the surface straight ALONG the grain, and converts it to something closer to end grain that can't "split"
@@aaronfuzion I watched a glue comparison video in the past year or so that found End Grain glueups to actually be STRONGEER than Face Grain, which went against all previous recommendations. Perhaps the soaking of glue into the wood means the glue travels farther into the wood to provide more surface to adhere to?
On the Miter joint, I think the physics part of it that BasTaart mentions is what is at play here and less about the end grain/face grain debate. While the board is trying to pull apart from the test, you have the inside portions of the joint pushing against each other acting as a small brace.
The most important ingredient of strength & Power , beyond any doubt , is ,definitely, Knowledge. Thanks always.
Great Video! Entertaining and informative. Very interesting results indeed. Based on other joint strength videos, I would have expected dowels to have been one of the stronger joints. You have used plain dowels. Maybe you could add an extra joint (in your suggested future joint tests) using fluted dowels? The extra surface area could make a difference and it would be interesting to see what the difference would be if any. Thank you
from the breakage, it looks like the dowel joint failed because it blew through the thin side wall. That suggests to me that the dowel to board ratio was too high. smaller diameter dowels would have done better.
I'd like to note that the differences between the dovetail and box joints has a lot to do with surface area and the glue. Early in the video the glue butt joint performed much better than expected. The smaller cutouts on the box joint had significantly more surface area for glue. I'd like to see tests where either the base or the end of the dovetail are equal to the box joint. I think that would pose some interesting results.
This is interesting! I NEED HELP to figure out what would be the strongest joint for a sturdy woodenbox to sit my refrigerator on. Top is. I want a top cover to attach to the sides of the box. Should I also put one on the bottom too? Thanks guys! :)
I would like to add , that the type & quality of the adhesive is an important & major factor in determining the strength of the joint. On the other hand, your demonstration is very impressive. As always, thanks.
My dad has been a finish carpenter for 40 years. I remember when he showed me how if you glue and clamp 2 pieces of wood and you went to break that piece of wood, it wouldn’t break on the glue seam. Wood glue is actually stronger than wood. Im assuming Mitre is strongest because you are glueing two identical pieces of wood/grain.
Great video! A couple of thoughts on the joints that surprised you:
1. Miter joint - this joint puts more surface area in contact because it's cut on the bias; more surface area = more strength.
2. Dovetail joint - the asymmetry of the tenon and mortise widths of the test joint makes me suspect that the smaller-cross- section tenons were the weak link. It would be interesting to compare strength of the style you tested to a more symmetrical one.
It is also because you have endgrain to endgrain, when you have endgrain to longgrain the longgrain will splitt apart because it is pulled sideways. Endgrain to endgrain will pull the wood fibers in the correct direction. The splines added was made of walnut that is a stronger material. To make it correct it would need at least 10-32 joints of each, statistically sort out differences in wood and amount of glue.
Well the mitter splints were a very hard wood so that def helped
It would be interesting to see the results of a dovetail joint that has the same number of pins and tails as the box joint did. Or at least closer to the same number.
I was thinking about that too. Also consider making the pins and tails roughly the same size. This is likely one of the reasons the box joint did so well.
@@stevesiefken6432 exactly. Who makes dovetails like the ones in this video? I know I've never done it that way. They're meant to be the same size. As soon as I saw those tiny dovetails I laughed.
Agreed, it is the square area of surface that the glue bonds and as it increases s does the relative strength.
agreed, i think the thin pins were the weak point in this test.. though very sexy!
@@popparock6506 The pins didn't break, though, so they weren't the weak point. The glue turned loose and allowed the pins to split their way out of the tails. There just needs to be more glue surface so the glue has more strength overall. With so little pin-tail surfaces touching, the glue joint was barely better than a butt joint. More pins will provide that surface area regardless of their size proportional to the tails. Increasing the number of pins will necessarily reduce the size of the tails, though.