I remember an older guy giving me GOOD ADVICE when I started working in coal prep plants out of high school with only growing up on a farm with a dad who knew a little about everything and alot about somethings. " If a guy is picking on you and insulting you, he thinks you're a good worker and likes you, and if they don't talk to you at all, they don't like you. Best advice for young workers.......except for "If you dont have anything to do, find something to do (even of its picking up trash.) At the very least, look worried and in a hurry!" 😂 Which really should be on a t shirt
JKM dovetail jig is a game changer for me. So far I have hand cut approximately 30 boxes (drawers) with the jig and it has become a necessity for me. I was travelling for work and was cutting some dovetails without my JKM jig and it made me understand just how much I love it. Keep up the good work John. Best youtube purchase I ever made.
This is what you call great content. I personally appreciate the time you took to make this videos and link the paper. I have a glue up I’m doing this week and needed more clamps. And it’s always guess work for me. This cleared everything up and provided me with an understanding of what to do going forward. Thanks you.
It seems you have force and pressure mixed up in the beginning. Clamps generate force (lbs) not pressure (psi). Dividing force by area gives pressure. Your calculation for 46.5 clamps was correct. Most furniture builders aren't getting hundreds of psi in their glue joints. When you switched to suggesting 2.9 clamps, I think you were saying that 3 clamps is required to evenly distribute the pressure over the joint. With 3 clamps at 400 lbs, your joint pressure would be 38 psi. (1200 lbs/31 sq.in) Since you're never going to get hundreds of psi of clamp pressure, you could skip the first 10 minutes of confusing explination and instead suggest that you space clamps at 2x the board's width. (Eg., every 8 inches for a 4 inch board). Same rule for cauls.
Glad to see other picked up on this right away... sadly, this kind of error brings some distrust to the whole presentation, and it would not take much to edit this video, with the corrections needed, and really make it work.
This is so interesting because all this time I've been practicing these things, thick cauls= less clamps, super thin glue ups need a ton of clamps, and I never really knew why. I'm super happy that's been explained now, I've learned a lot today
400 lbs of pressure spread over 10 square inches = 400lbs /10 " = 40 lbs/1"; spread over 100 square inches = 400 lbs / 100 = 4lbs/1". The critical factors is the thickness of the glue line and the absorption of the glue into the wood/ the adhesion of the glue with the wood. Good video for things to consider when clamping.
I can't wait to see all the parodies of this video. All I got was.... "Blaa blaa blaa, clamps!" But I am just teasing you. I do thank you for taking the time and going through all this so thoroughly. We love you Katz.
I’m with you on the Bessey and Jet clamps. What a pain to adjust but they are great clamps. My favorite though are the Jorgensens cabinet clamps. The Taylor look very much like them actually and I’ll check them out. Great content that I will be passing along a brand new woodworker friend of mine.
Sorry, but for those outside of the US, who is William Walker. The William Walker that I know of is a local hero with a pub in Winchester named after him: en.wikipedia.org/wiki/William_Walker_(diver)
Johnathan, i wanted to say thank you for the educational video. I was just reading about this exact thing in WWJ last night. Im rather new and about to attempt my first 7’ long glue up. The math makes me feel better about “knowing” how many clamps i need. I read a few of the “smarter than Katz” comments and was blown away by their arrogance!! If you dont like the video dont watch it. You always provide great insight for me! Im about to buy am ez up to spray my first project. Once again, I learned it from you! Keep it up jedi, Im learning more everyday.
We watched because we thought we might learn something. I've been a cabinet maker and boat builder for 50years but I'm still learning. What we learnt was the man is a bit misguided and will through his confidentvdelivery fool many.
Awesome vid man. thanks very helpful, I was glad to hear you say its hard for you as well to get the parallel clamps open and closed, I always thought it was just me. and I'm definitely purchasing the tay tools
I see a cam clamp in the video, however you didn't talk about them. Also, a convex caul can help by using fewer clamps over a long surface. Sometimes only needing two clamps at the ends.
Thanks so much for the information! I was wondering about the quality of the Taytools parallel clamps. I know you have highly recommended his products before, but I'm thankful you mentioned how much you love them. Love your content!!
I’ll have to give her Taylor Tools clamps a good luck because I like supporting small businesses. While I’ve not used the Taylor Tools parallel clamps I do like my Jets. I have absolutely no problems setting them up and always do a dry fit first. That prevents any bog adjustments after the glue is applies. I agree that Jets are expensive but all mine were bought on some great sales. That’s the best way to buy them.
Thanks very much. Useful information. I am a relatively new wood worker. Really love to make things but was worried about adding too much or too little glue. Found this really good. Cheers
@ 4:35, and the gloves come off! I bet I can beat you both though. After all, being a front end technician, I probably lift the equivalent of four tons in tires every day, plus strut assemblies, steering gears, etc. Oh wait, I haven't done that since 2012 before my neck surgery sidelined me. I'll tap out now. Very informative video Jonathan.
Thank you for all the info. You said that squeeze clamps are about 400 psi. But, how can you tell how much pressure you're applying? Say you want to apply 250 psi with a squeeze clamp, how can you tell when to stop applying pressure?
What is optimum pounds per square inch? Also I think Jonathan is confusing psi and the "pounds of force". Imagine you squeezed a kitchen scale with a clamp, regardless of the size of the face of the clamp or scale you will get the same number (let me know if I'm wrong, but I think this type of force is how manufacturers advertise clamps). Psi is the force over an area, if I apply 10lbs of force with my thumb (10psi) to your skin it won't hurt. But, that 10 pounds on the point of a pin (6000psi) would hurt a lot....
You apply a force, but stress is what matters. A clamp, tightened in the same fashion, will apply a fixed force (pounds or Newtons). That force acts upon an area, which gives you a stress / pressure (psi or Pascals). Technically the clamp is actually applying a pressure of the clamping force divided by the contact area of the clamp head (you can't actually apply just a force, because you have to have an area to apply it to), but it's easier to work with if you just use the force. For the calculations here, we're making a key assumption that the wood is a rigid body, meaning that it doesn't deform and merely transfers the force (radiating outward at 45 degrees). Of course, that assumption isn't always that realistic, which is why we use clamping cauls to help distribute the force evenly and prevent denting the surface due to excessive localized force. Ultimately, it's simplest if you only concern yourself with three numbers. Required stress, glue surface area, and clamp force. Required stress times the glue surface area divided by clamp force will tell you how many clamps you need. You could work with the pressure a clamp generates on the face of the clamp, but you would just end up having to cancel out the face area anyway, so working directly with force simplifies the calculation. This doesn't cover the even distribution of force, which has to do with clamp spacing, stiffness of the wood, cauls etc., but it gets you to how many clamps you need and, outside of oddly shaped glue ups, just evenly spacing the appropriate number of clamps should get you where you need to be. The only time I can think of when this really doesn't apply is with extreme aspect ratios, like when working with something really long but thin (behave everyone). When gluing on hardwood edge trim the total area isn't that great, so you don't need that many clamps, but the piece is so thin that there isn't enough thickness for the force to "spread out" evenly. So either you use a thick caul to give the force more thickness to work with or you use lots of weaker clamps spaced closer together (which is why the comparitively weak bandy clamps work so well for this application). Maybe that was helpful to someone? I kind of just felt like talking about force and stress for a bit.
You apply a force, but stress is what matters. A clamp, tightened in the same fashion, will apply a fixed force (pounds or Newtons). That force acts upon an area, which gives you a stress / pressure (psi or Pascals). Technically the clamp is actually applying a pressure of the clamping force divided by the contact area of the clamp head (you can't actually apply just a force, because you have to have an area to apply it to), but it's easier to work with if you just use the force. For the calculations here, we're making a key assumption that the wood is a rigid body, meaning that it doesn't deform and merely transfers the force (radiating outward at 45 degrees). Of course, that assumption isn't always that realistic, which is why we use clamping cauls to help distribute the force evenly and prevent denting the surface due to excessive localized force. Ultimately, it's simplest if you only concern yourself with three numbers. Required stress, glue surface area, and clamp force. Required stress times the glue surface area divided by clamp force will tell you how many clamps you need. You could work with the pressure a clamp generates on the face of the clamp, but you would just end up having to cancel out the face area anyway, so working directly with force simplifies the calculation. This doesn't cover the even distribution of force, which has to do with clamp spacing, stiffness of the wood, cauls etc., but it gets you to how many clamps you need and, outside of oddly shaped glue ups, just evenly spacing the appropriate number of clamps should get you where you need to be. The only time I can think of when this really doesn't apply is with extreme aspect ratios, like when working with something really long but thin (behave everyone). When gluing on hardwood edge trim the total area isn't that great, so you don't need that many clamps, but the piece is so thin that there isn't enough thickness for the force to "spread out" evenly. So either you use a thick caul to give the force more thickness to work with or you use lots of weaker clamps spaced closer together (which is why the comparitively weak bandy clamps work so well for this application). Maybe that was helpful to someone? I kind of just felt like talking about force and stress for a bit.
Well I don't know bout anyone else but I'm positive I'll never do the math on clamping lol...I go to squeeze out an back off a touch, it's working so far perfectly... parallel clamps are my favorite Forsure..I just look at the project and just evenly put the clamps on, I guess in 3rds if you will.. F clamps im not a fan off, they like to crawl off whatever i try to clamp, wonder if im the only lol...I think people think you gotta just crank clamps down when its the worst thing you can do...great info John as always...
Thanks for the informative video! You really give a great wealth of information and the links to geek out of you want to. I've always wondered if i was clamping down on my stuff to hard. I've been doing it well enough to get squeeze out but how much is enough. 😀
You’re such a geek 😉 This is a great video. All the videos I’ve watched give really simple info (too simple) and basically say ‘that’s the way it is’, without going into any detail. Thankfully, the World’s strongest man came to the rescue. Nice one Governor 👍
I'm just now seeing this 3yr old video. TayTools doesn't stock those parallel clamps anymore. Any chance you know the manufacturer? I've got a bunch of the Bessey's and notice the same, annoying sticking issue. Looking for something more friendly.
I learned some useful stuff there, and thanks for clarifying who the heck William Walker was about. I'd paused the video to Google and was getting all sorts of strange hits, none of which had anything to do with your reference. When it comes to shavings those videos Japanese craftsmen making 12" wide continuous wafer thin shavings about six feet long take some beating.
You have some of your units mixed up at the beginning. But what's written next to the diagram starting about 7:00 is correct. Glue joints care about pressure; i.e., force per unit area. In the U.S. this is usually specified in pounds per square foot (PSI). Franklin and other glue manufacturers list the recommended pressure to be used with their glues (in PSI). On the other hand, clamps exert force, typically expressed in pounds. Clamp manufacturers all rate their products in terms of force; i.e., how many pounds they can apply. Talking about pressure (PSI) in terms of a clamp is pretty meaningless. A clamp tightened to 300 lbs of force with its jaws touching an area 1/2" x 1" will be exerting a pressure of PSI of 600 PSI at that contact point. The same clamp tightened the same amount, but with the jaws oriented differently so that the contact patch is 1" x 1" will now be exerting 300 PSI on the contact point. But whatever the PSI happens to be at the contact point, it has little to do with the pressure experienced at the glue joint. As the diagram shows, you multiply the width of the joint in inches by its thickness (in inches) to come up with the joint area in square inches. Then multiply that by the desired pressure in PSI, to come up with the needed total *force*, in pounds. Divide by the force per clamp (not pressure per clamp), to get the minimum number of clamps needed (although you many need more if you have narrow boards and don't use cauls in order to meet the 45 degree criterion). FYI, for edge banding, since I'm usually banding more than one board, I just do two at a time and butt them together with the two bands touching, so the clamping points are far from the bands and the 45 degree thing is satisfied.
Its great info in terms of PSI but in the world of woodworking or general clamp use there is no psi measurement on each clamp and even if there was the glue-up time is generally too short with titebond 1,2,3 snd such.
A little geometry trick I realized watching this. If you space your clamps by 2x the width of narrowest piece, you’ll have full coverage (assuming each clamp can reach the total needed clamping pressure locally). I think.
Nice video! What do you think about making your clamping calls slightly concave, so as you squeeze in the middle it pushes the pressure to the outside. Now I'm going to have go do some calculations.
I'm more confused after watching this. I think you end up with the right number of clamps in the end, but I don't see any clamps rated in PSI. They're simply rated in pounds. You just take those pounds, distributed over the area of the triangle and width / thickness of the board, and that's it.
He confuses psi and pounds of force badly, and got the math and mechanics/physics very wrong. The takeaway I got from this was, if he’s right about the target psi, I’ll never be able to over clamp a joint within reason.
@@youwantjosh If he's right about the target PSI you'll only reach the target pressure on the smallest of joints. Manufacturers of engineered wood products actually use clamping pressures this high, but they don't use PVA glue and pipe clamps.
Great video man. I was just recently looking up info about all the different kind of clamps. Thanks for the detailed info. Do you use aluminum bar clamps much? I was only able to to find info here and there about them. Thanks!
I got the Tay Tools parallel clamps and I love them. However when I release the clamp the it leaves little dents on the clamps metal bar, is this normal? They still adjust really easily.
Thanks for sharing this info! Great stuff. Quick question. How do you know you have an even amount of force applied to each clamp when using multiple clamps? Is it just by feel or is there another indicator? Thanks!
I'm a beginner so this is very helpful. Maybe it's because I'm a beginner or because I'm in the UK that I've never heard of a call? Cole? However it's spelt, what is it?
Fantastic presentation, but I have 3 questions:1. How does the math change if you’re laminating a dozen 2”x2” boards? Put another way, you explained it wonderfully for one glue line, what happens with 2 or more glue lines? 2. How much curvature does a caul need to give you the target clamping pressure? (Related: does the type of wood used in the caul impact how curved a surface is required on the caul?) 3. How much glue is the right amount?
Jonathan Katz-Moses I’ll let you know. I ordered some. I like it when folks think outside the box and Woodpeckers seem to do a lot of it. It’s a huge hassle for me to set up an extra set of clamps and cauls to keep things flat. Yeah, they’re expensive, but if they replace several clamps and time at glue up, then I’ll be happy. They’re a “one time tool” so there won’t be many of them around. I’ll report back when they arrive late summer.
I wrap the Bessey clamps and others with smooth shiny handles with friction tape. Makes them significantly easier to tighten. Like the continued math related woodworking.
@@katzmosestools Thanks for the quick reply. And it's always nice to see youtubers reading comments. It's a very beautiful watch, I'm thinking of buying a watch and this design is right in my valley
@@katzmosestools One could possibly use the clamp formula as justification to your significant other to purchase more clamps.... "See honey, it says I need 44 clamps for this 8x15 panel - off to the woodworking store!"
Clamps do not generate pressure. Clamps generate force (pounds of force). The pressure at the joint is related to the force from each clamp added together and distributed across area the joint...Total Pounds of force generated from all the clamps divided by area of the joint would = the average PSI. The PSI at any given portion of the joint will be related to angle of adjacent clamps.
I remember an older guy giving me GOOD ADVICE when I started working in coal prep plants out of high school with only growing up on a farm with a dad who knew a little about everything and alot about somethings. " If a guy is picking on you and insulting you, he thinks you're a good worker and likes you, and if they don't talk to you at all, they don't like you. Best advice for young workers.......except for "If you dont have anything to do, find something to do (even of its picking up trash.) At the very least, look worried and in a hurry!" 😂 Which really should be on a t shirt
You are quickly becoming my favorite woodworking UA-camr. I love your style and the way you talk through things. Thanks for being you! ^_^
Finally!! More isn't always better. I think the more we glue up stuff the better handle we get on the process. Great info! Thanks for sharing!
JKM dovetail jig is a game changer for me. So far I have hand cut approximately 30 boxes (drawers) with the jig and it has become a necessity for me. I was travelling for work and was cutting some dovetails without my JKM jig and it made me understand just how much I love it. Keep up the good work John. Best youtube purchase I ever made.
Thats awesome!
This is what you call great content. I personally appreciate the time you took to make this videos and link the paper. I have a glue up I’m doing this week and needed more clamps. And it’s always guess work for me. This cleared everything up and provided me with an understanding of what to do going forward. Thanks you.
Thanks for sharing
You're giving Will about 4 more psi than I would. Great stuff, bro!
It seems you have force and pressure mixed up in the beginning. Clamps generate force (lbs) not pressure (psi). Dividing force by area gives pressure. Your calculation for 46.5 clamps was correct. Most furniture builders aren't getting hundreds of psi in their glue joints. When you switched to suggesting 2.9 clamps, I think you were saying that 3 clamps is required to evenly distribute the pressure over the joint. With 3 clamps at 400 lbs, your joint pressure would be 38 psi. (1200 lbs/31 sq.in) Since you're never going to get hundreds of psi of clamp pressure, you could skip the first 10 minutes of confusing explination and instead suggest that you space clamps at 2x the board's width. (Eg., every 8 inches for a 4 inch board). Same rule for cauls.
Yep, rating clamps by PSI makes no sense, which is why clamp manufacturers don't so.
Yes, the video totally butchered the math, and the math was the point of the video.
I just couldn't get to the end because of that pressure/force confussion...
Yup, he's wrong. But who needs to be right, when you can be wrong with such CONFIDENCE?
Glad to see other picked up on this right away... sadly, this kind of error brings some distrust to the whole presentation, and it would not take much to edit this video, with the corrections needed, and really make it work.
Great information. When I started woodworking I was constantly over tightening and it absolutely makes the joint less strong.
Adding a little paste wax to parallel clamp bars completely solves the difficulty opening/closing em. and it stops glue from sticking to em.
This is so interesting because all this time I've been practicing these things, thick cauls= less clamps, super thin glue ups need a ton of clamps, and I never really knew why. I'm super happy that's been explained now, I've learned a lot today
There’s a lot I know I don’t know. Videos like this make me realize there’s a lot I don’t know I don’t know. Great video! Thanks!
Cheers!
400 lbs of pressure spread over 10 square inches = 400lbs /10 " = 40 lbs/1"; spread over 100 square inches = 400 lbs / 100 = 4lbs/1". The critical factors is the thickness of the glue line and the absorption of the glue into the wood/ the adhesion of the glue with the wood. Good video for things to consider when clamping.
Awesome video and really useful. You’re quickly becoming my go to channel
Greatly helpful video. I love his style.
I can't wait to see all the parodies of this video. All I got was.... "Blaa blaa blaa, clamps!"
But I am just teasing you. I do thank you for taking the time and going through all this so thoroughly. We love you Katz.
I just spat my drink out 🤯 Mind blown.
I’m with you on the Bessey and Jet clamps. What a pain to adjust but they are great clamps. My favorite though are the Jorgensens cabinet clamps. The Taylor look very much like them actually and I’ll check them out. Great content that I will be passing along a brand new woodworker friend of mine.
Jonathan this was a great video. Very well researched and presented. I learned a lot, thank you.
Very useful information
"William Walker could only get 5 or 6" 🤣🤣🤣
Sorry, but for those outside of the US, who is William Walker. The William Walker that I know of is a local hero with a pub in Winchester named after him: en.wikipedia.org/wiki/William_Walker_(diver)
@@chrislaing7153 ua-cam.com/channels/ievvwx_-UU-rP28103rUCw.html
Johnathan, i wanted to say thank you for the educational video. I was just reading about this exact thing in WWJ last night. Im rather new and about to attempt my first 7’ long glue up. The math makes me feel better about “knowing” how many clamps i need. I read a few of the “smarter than Katz” comments and was blown away by their arrogance!! If you dont like the video dont watch it. You always provide great insight for me! Im about to buy am ez up to spray my first project. Once again, I learned it from you! Keep it up jedi, Im learning more everyday.
We watched because we thought we might learn something. I've been a cabinet maker and boat builder for 50years but I'm still learning. What we learnt was the man is a bit misguided and will through his confidentvdelivery fool many.
Very informative and useful Jonathan
Not going to lie, I always crank em' down. Never thought to sit and so the math on that. Good video. Thank you, Johnathan! :)
Awesome vid man. thanks very helpful, I was glad to hear you say its hard for you as well to get the parallel clamps open and closed, I always thought it was just me. and I'm definitely purchasing the tay tools
For a minute there I thought that you were trying to convince me that I have enough clamps...
Awesome video. Tons of great info that is worth it's weight in gold.
Mc Katz-Moses dropping them bars at 16:37
This guy is the woodworking sensei
I see a cam clamp in the video, however you didn't talk about them.
Also, a convex caul can help by using fewer clamps over a long surface. Sometimes only needing two clamps at the ends.
Fantastic tips, Jonathan! Thanks a lot!!! 😃
Stay safe there with your family! 🖖😊
Thanks so much for the information! I was wondering about the quality of the Taytools parallel clamps. I know you have highly recommended his products before, but I'm thankful you mentioned how much you love them. Love your content!!
I’ll have to give her Taylor Tools clamps a good luck because I like supporting small businesses. While I’ve not used the Taylor Tools parallel clamps I do like my Jets. I have absolutely no problems setting them up and always do a dry fit first. That prevents any bog adjustments after the glue is applies. I agree that Jets are expensive but all mine were bought on some great sales. That’s the best way to buy them.
Wow! That is a lot of info but that is some well thought out stuff. So many options out there and that was helpful!
Thanks very much. Useful information. I am a relatively new wood worker. Really love to make things but was worried about adding too much or too little glue. Found this really good. Cheers
Another great video, thanks Katz.
I’m a WMU grad. Who knew a prof there did a study on gluing?! Pretty cool.
Hey me too! I also worked on the engineering campus for a few years after college. Great school!
Nice video. Thanks
Thanks again for costing me more money! Seriously though, great video with lots of great info!
“...let’s talk about how pressure is allocated...” - I need you to talk to my boss....
@ 4:35, and the gloves come off! I bet I can beat you both though. After all, being a front end technician, I probably lift the equivalent of four tons in tires every day, plus strut assemblies, steering gears, etc. Oh wait, I haven't done that since 2012 before my neck surgery sidelined me. I'll tap out now.
Very informative video Jonathan.
Those taytool parallel clamps look and act almost identical to the Jorgensen clamps which I really like, they are super smooth.
Thanks buddy!
Really....i love the Jet ones. Hate the bessey parallel clamps for adjusting. Should try the taytools ones
I always enjoy your videos. Just wish there was a double-like button.
Thank you for all the info. You said that squeeze clamps are about 400 psi. But, how can you tell how much pressure you're applying? Say you want to apply 250 psi with a squeeze clamp, how can you tell when to stop applying pressure?
What is optimum pounds per square inch? Also I think Jonathan is confusing psi and the "pounds of force". Imagine you squeezed a kitchen scale with a clamp, regardless of the size of the face of the clamp or scale you will get the same number (let me know if I'm wrong, but I think this type of force is how manufacturers advertise clamps). Psi is the force over an area, if I apply 10lbs of force with my thumb (10psi) to your skin it won't hurt. But, that 10 pounds on the point of a pin (6000psi) would hurt a lot....
You apply a force, but stress is what matters. A clamp, tightened in the same fashion, will apply a fixed force (pounds or Newtons). That force acts upon an area, which gives you a stress / pressure (psi or Pascals). Technically the clamp is actually applying a pressure of the clamping force divided by the contact area of the clamp head (you can't actually apply just a force, because you have to have an area to apply it to), but it's easier to work with if you just use the force. For the calculations here, we're making a key assumption that the wood is a rigid body, meaning that it doesn't deform and merely transfers the force (radiating outward at 45 degrees). Of course, that assumption isn't always that realistic, which is why we use clamping cauls to help distribute the force evenly and prevent denting the surface due to excessive localized force.
Ultimately, it's simplest if you only concern yourself with three numbers. Required stress, glue surface area, and clamp force. Required stress times the glue surface area divided by clamp force will tell you how many clamps you need. You could work with the pressure a clamp generates on the face of the clamp, but you would just end up having to cancel out the face area anyway, so working directly with force simplifies the calculation.
This doesn't cover the even distribution of force, which has to do with clamp spacing, stiffness of the wood, cauls etc., but it gets you to how many clamps you need and, outside of oddly shaped glue ups, just evenly spacing the appropriate number of clamps should get you where you need to be. The only time I can think of when this really doesn't apply is with extreme aspect ratios, like when working with something really long but thin (behave everyone). When gluing on hardwood edge trim the total area isn't that great, so you don't need that many clamps, but the piece is so thin that there isn't enough thickness for the force to "spread out" evenly. So either you use a thick caul to give the force more thickness to work with or you use lots of weaker clamps spaced closer together (which is why the comparitively weak bandy clamps work so well for this application).
Maybe that was helpful to someone? I kind of just felt like talking about force and stress for a bit.
You apply a force, but stress is what matters. A clamp, tightened in the same fashion, will apply a fixed force (pounds or Newtons). That force acts upon an area, which gives you a stress / pressure (psi or Pascals). Technically the clamp is actually applying a pressure of the clamping force divided by the contact area of the clamp head (you can't actually apply just a force, because you have to have an area to apply it to), but it's easier to work with if you just use the force. For the calculations here, we're making a key assumption that the wood is a rigid body, meaning that it doesn't deform and merely transfers the force (radiating outward at 45 degrees). Of course, that assumption isn't always that realistic, which is why we use clamping cauls to help distribute the force evenly and prevent denting the surface due to excessive localized force.
Ultimately, it's simplest if you only concern yourself with three numbers. Required stress, glue surface area, and clamp force. Required stress times the glue surface area divided by clamp force will tell you how many clamps you need. You could work with the pressure a clamp generates on the face of the clamp, but you would just end up having to cancel out the face area anyway, so working directly with force simplifies the calculation.
This doesn't cover the even distribution of force, which has to do with clamp spacing, stiffness of the wood, cauls etc., but it gets you to how many clamps you need and, outside of oddly shaped glue ups, just evenly spacing the appropriate number of clamps should get you where you need to be. The only time I can think of when this really doesn't apply is with extreme aspect ratios, like when working with something really long but thin (behave everyone). When gluing on hardwood edge trim the total area isn't that great, so you don't need that many clamps, but the piece is so thin that there isn't enough thickness for the force to "spread out" evenly. So either you use a thick caul to give the force more thickness to work with or you use lots of weaker clamps spaced closer together (which is why the comparitively weak bandy clamps work so well for this application).
Maybe that was helpful to someone? I kind of just felt like talking about force and stress for a bit.
How do you know the PSI needed depending on tree type? Is there a source somewhere I can find this info?
Well I don't know bout anyone else but I'm positive I'll never do the math on clamping lol...I go to squeeze out an back off a touch, it's working so far perfectly... parallel clamps are my favorite Forsure..I just look at the project and just evenly put the clamps on, I guess in 3rds if you will.. F clamps im not a fan off, they like to crawl off whatever i try to clamp, wonder if im the only lol...I think people think you gotta just crank clamps down when its the worst thing you can do...great info John as always...
Taytools appears to no longer have parallel clamps unfortunately. Still loving yours? Might hold out in case they come back in stock!
Where did you get your marking knife from Jonathan?
Thanks for the informative video! You really give a great wealth of information and the links to geek out of you want to. I've always wondered if i was clamping down on my stuff to hard. I've been doing it well enough to get squeeze out but how much is enough. 😀
Very interesting, thank you Jonathan!
Thank you it was well explain again
I use 4 way clamps, any tip about how much force i need do to glue woods like a purple heart? Abraço.
What I was wondering after this. is what about say a butcher block? multiple seams?
You’re such a geek 😉
This is a great video. All the videos I’ve watched give really simple info (too simple) and basically say ‘that’s the way it is’, without going into any detail. Thankfully, the World’s strongest man came to the rescue. Nice one Governor 👍
I'm just now seeing this 3yr old video. TayTools doesn't stock those parallel clamps anymore. Any chance you know the manufacturer? I've got a bunch of the Bessey's and notice the same, annoying sticking issue. Looking for something more friendly.
Good stuff.
Agree! Easy to learn from!
So...halfway through I questioned whether or not I’m smart enough to be a woodworker. I’m sticking with, “A lot and tight.”
I learned some useful stuff there, and thanks for clarifying who the heck William Walker was about. I'd paused the video to Google and was getting all sorts of strange hits, none of which had anything to do with your reference. When it comes to shavings those videos Japanese craftsmen making 12" wide continuous wafer thin shavings about six feet long take some beating.
You have some of your units mixed up at the beginning. But what's written next to the diagram starting about 7:00 is correct.
Glue joints care about pressure; i.e., force per unit area. In the U.S. this is usually specified in pounds per square foot (PSI). Franklin and other glue manufacturers list the recommended pressure to be used with their glues (in PSI).
On the other hand, clamps exert force, typically expressed in pounds. Clamp manufacturers all rate their products in terms of force; i.e., how many pounds they can apply. Talking about pressure (PSI) in terms of a clamp is pretty meaningless. A clamp tightened to 300 lbs of force with its jaws touching an area 1/2" x 1" will be exerting a pressure of PSI of 600 PSI at that contact point. The same clamp tightened the same amount, but with the jaws oriented differently so that the contact patch is 1" x 1" will now be exerting 300 PSI on the contact point. But whatever the PSI happens to be at the contact point, it has little to do with the pressure experienced at the glue joint.
As the diagram shows, you multiply the width of the joint in inches by its thickness (in inches) to come up with the joint area in square inches. Then multiply that by the desired pressure in PSI, to come up with the needed total *force*, in pounds. Divide by the force per clamp (not pressure per clamp), to get the minimum number of clamps needed (although you many need more if you have narrow boards and don't use cauls in order to meet the 45 degree criterion).
FYI, for edge banding, since I'm usually banding more than one board, I just do two at a time and butt them together with the two bands touching, so the clamping points are far from the bands and the 45 degree thing is satisfied.
Do you like the taytools clamps better than bessey? I'm needing some more clamps for table tops, and value your opinion.
Yes. They're linked in the pinned comment
Now I need to go buy more clamps!
As a beginner, do you have a recommendation of amounts of each style clamps? Like, x amount of pipe clamps, x amount of F clamps, etc.
4 pipe clamps 2x 48 and 2 x 24, 4x parallel at 36 and 12 f style clamps mixed between 6 and 12 inches
Jonathan Katz-Moses thank you very much.
Its great info in terms of PSI but in the world of woodworking or general clamp use there is no psi measurement on each clamp and even if there was the glue-up time is generally too short with titebond 1,2,3 snd such.
A little geometry trick I realized watching this. If you space your clamps by 2x the width of narrowest piece, you’ll have full coverage (assuming each clamp can reach the total needed clamping pressure locally). I think.
Nice video! What do you think about making your clamping calls slightly concave, so as you squeeze in the middle it pushes the pressure to the outside. Now I'm going to have go do some calculations.
I'm more confused after watching this. I think you end up with the right number of clamps in the end, but I don't see any clamps rated in PSI. They're simply rated in pounds. You just take those pounds, distributed over the area of the triangle and width / thickness of the board, and that's it.
Clamps are indeed not rated in PSI, and it's kinda meaningless to rate them with PSI. See my comment for a detailed explanation.
He confuses psi and pounds of force badly, and got the math and mechanics/physics very wrong. The takeaway I got from this was, if he’s right about the target psi, I’ll never be able to over clamp a joint within reason.
Led Zepaholic metric is good. Do you know if 10N/cm^2 is pretty normal, or how to get the correct value for particular glues/woods?
@@youwantjosh If he's right about the target PSI you'll only reach the target pressure on the smallest of joints. Manufacturers of engineered wood products actually use clamping pressures this high, but they don't use PVA glue and pipe clamps.
That's all well and good, but how about the pressure / force for veneering? o.O
Great video man. I was just recently looking up info about all the different kind of clamps. Thanks for the detailed info. Do you use aluminum bar clamps much? I was only able to to find info here and there about them. Thanks!
The glue I use says on the bottle 100 to 150 PSI for light woods and for dense woods 120 to 160 PSI.
What about the 4 way clamps?
IDK who William Walker, is but I love that dry comedy of exaggering the JKM PSI capabilities and throwing some serious shade at William Walker's PSI
Poor Will Walker. LOL
Where does timber dogs fit into all of this? I am on a very strict budget for I almost have to make my own or use what I have, hence the question.
Okay, now do strap clamps!! I think most of us just wing it. This information helps. Thanks Jonathan.
I got the Tay Tools parallel clamps and I love them. However when I release the clamp the it leaves little dents on the clamps metal bar, is this normal? They still adjust really easily.
As someone who’s about to order some, how do they compare to the Irwin’s that Lowe’s sales. They look like those but unbranded.
Does spacers change the pressure when trying not to mark the wood
Yes and I discussed it in this video
Thanks for sharing this info! Great stuff. Quick question. How do you know you have an even amount of force applied to each clamp when using multiple clamps? Is it just by feel or is there another indicator? Thanks!
I'm a beginner so this is very helpful. Maybe it's because I'm a beginner or because I'm in the UK that I've never heard of a call? Cole? However it's spelt, what is it?
Fantastic presentation, but I have 3 questions:1. How does the math change if you’re laminating a dozen 2”x2” boards? Put another way, you explained it wonderfully for one glue line, what happens with 2 or more glue lines? 2. How much curvature does a caul need to give you the target clamping pressure? (Related: does the type of wood used in the caul impact how curved a surface is required on the caul?) 3. How much glue is the right amount?
how about taping culls. Is that not also clamping?
Thanks Jonathan! Have you seen the Clampzilla from Woodpeckers?
Yes. Seems like a lot of gadget for a lot of money
Jonathan Katz-Moses I’ll let you know. I ordered some. I like it when folks think outside the box and Woodpeckers seem to do a lot of it. It’s a huge hassle for me to set up an extra set of clamps and cauls to keep things flat. Yeah, they’re expensive, but if they replace several clamps and time at glue up, then I’ll be happy. They’re a “one time tool” so there won’t be many of them around. I’ll report back when they arrive late summer.
I wrap the Bessey clamps and others with smooth shiny handles with friction tape. Makes them significantly easier to tighten. Like the continued math related woodworking.
How do you know how much PSI you’re adding?
Can you explain where is that 45 degree info coming from?
im confused about what clamps are used for maple. i see pipe clamps can go to 1000lbs, but maple requires 1200. how does that work?
LOL. That Walker comment... You sir, are savage! :D Sigh. Too bad I can only subscribe ONCE.
lol thank you Katz . yes at 67 i am squishy lol ah no one see me now days hit the invisible state . i did wonder about those clamps n how many
anybody know where to source the heavier duty f clamps?
Why isn't anyone talking about how he drew a perfectly straight line across that board at @10:12
Use your finger as a guide against the edge 👍
Does anyone know what watch he's wearing?
Seiko 5 sport
@@katzmosestools Thanks for the quick reply. And it's always nice to see youtubers reading comments.
It's a very beautiful watch, I'm thinking of buying a watch and this design is right in my valley
One simply does not ever have enough clamps.
NEVER!
@@katzmosestools One could possibly use the clamp formula as justification to your significant other to purchase more clamps.... "See honey, it says I need 44 clamps for this 8x15 panel - off to the woodworking store!"
I feel sorry I only have 3 sash clamps, 3 g clamps, and 4 quick pressure clamps.
Clamps are rated in pounds, not PSI. The PSI is the force divided by area, so the same clamp over a larger area will yield a *lower* PSI.
Squishy meat bag! Haha! Thanks for the laugh
🤣🤣
Rick and Morty special hahahaha
I was wondering where I had head that from lmao
My wife heard that and said “is that what they call boobs” 😂
🤣🤣
I would've never imagined that Jimmy Kimmel had such extensive woodworking knowledge.
Clamps do not generate pressure. Clamps generate force (pounds of force). The pressure at the joint is related to the force from each clamp added together and distributed across area the joint...Total Pounds of force generated from all the clamps divided by area of the joint would = the average PSI.
The PSI at any given portion of the joint will be related to angle of adjacent clamps.
what kind of watch?
Seiko 5 sport
How many PSI is Danny DiVito?
You had me at "squishy meatbags"