You are amazing Sir. You made it so easy. I am watching this for the second time from my saved videos. I just bought a circular saw and would like to try it out on a wider plywood
Great video Issac! Your explanation was so easy to follow and now I am armed with the information needed to tackle some new creations. Thank you so much!
Well done sir! I was searching for kerf cuts in metal for a welding project I am doing. There is not much information on YT on this subject but your video is such that I should be able to change values and make the cuts I need without any guesswork. This should help with my project immensely. Thank you for posting!
For those of us who never did well in math, this seems very complicated until you did such a beautiful job explaining each step. I'm looking at comments from others and getting myself more and more confused, so I'll slow down and take each comment into consideration when planning my cuts. Seems daunting, but I'm sure it's relatively easy as soon as you actually do it. Thanks!
What an amazing video! Ive been looking up kerf bending techniques and gotten a bit frustrated by how many people just have a kind of eye balling it approach to spacing the cuts, but i Love how it just makes so much SENSE the way you explained it! Thank you for this cool resource!
And they said we would never use this type of math. Pfffft. You did a great job explaining everything. Just the kind of info and instruction was looking for. THANK YOU!
I liked your video, and it made me think about something I really hadn't put much thought into before. I usually just cut a bunch of kerfs and move on, so thanks. If you want to greatly simplify your math... Circumference = C, radius = R, board thickness = T: C1 = 2piR1, C2 = 2piR2, R1 = R2 + T, C1 - C2 = 2piR1 - 2piR2 = 2pi(R2 + T) - 2piR2 = 2piR2 + 2piT - 2piR2 = 2piT In other words, it doesn't matter the size of the circle, the difference in circumference between two circles that share the same center and are T thickness apart is always 2piT. In your example of a 12mm board: 2 * 3.14 * 12mm = 75.36mm. We want a quarter of that for our 90deg bend. 75.36mm / 4 = 18.84mm --> your answer in the video. For a 90deg bend, the answer will always be: (2piT)/4 = 0.5piT for a board thickness of T. A 180deg bend will be piT, and so on.
There is almost always an easier way. Most of the time, with some experience, just curring works fine. But the video was about exploring the exact way of doing it. Is it overkill? maybe yes hahaha
Nice, simple explanation. One observation: Dividing 110 by 19, as you've done, means 19 grooves with 18 sections of 5.8mm between them, plus (half of) the two outer cuts, which comes to 105.4mm. The remaining 4.6mm at the ends do not bend, they are part of the rest of the board which is straight, and this may be significant in some situations. To have the last bend right at the end of the curve, you'll need to place the outermost grooves at the ends of the 110mm piece and divide the remainder by 18, i.e.: (110-2)/18=6mm.
hahaha....yes yes...well spotted. The fact is that the difference with one groove will be negligible. It is only a 5% error when Im quite certain the error on my hand saw is higher :-)
Hiya, I am having trouble understanding this. Could you possibly try and explain it better? "plus (half of) the two outer cuts, which comes to 105.4mm"- i dont quite understand this part and the last part. Thank you so much!
This is excellent! My wife found a little bathroom trash can for $300 that I offered to make for her. I wish I could get my hands on a CNC router to do the cuts accurately and fast. Anyway, I really appreciate the math. Well done!
i was searching for calculations explained and thanks to this video it doesnt look so complicated anymore,great video and thanks again it helped alot ! :)
Good content in this video. Very logical! This will help me with the shop math. I need to make large round table skirt now I have the formula for success. Thanks!
I'm amazed that you traced and measured the final product on your tablet! It would never occur to me to do that instead of using paper and pencil. I am old fashioned. Great video!
Your video is nicely done. The math is straight forward. The only thing missing is how deep should the cut be. I know there are zillion types of wood out there so it is nearly impossible to detail out. I guess I would have to try to cut pieces of wood that I normally work with, and do some trial and error to determine the depth of cut. Many thanks for putting this video together.
cool - thank you :-) I have a little input on the bending..... before cutting the grooves, make sure that the growing lines of the wood in the last layer (the outer Parameter) are going with the bend ;-) thus the fibres can stretch. if the look across the bending, the wood will crack - oops built couple of drums and this was the first thing I learnt ;-) thougt it might help
I wasn't aware that the layers of ply stretch at all. However, now that I think about it, it makes total sense. Steam or hot water also works to avoid breaks. Also, I hear tell from someone who's done this for 50 years that adding liquid fabric softener (like for clothing) to the hot water makes bending even easier.
Thanks! I need to do some kerfing, and I've been looking at video after explanation after... and none of them showed that it's actually a simple calculation that I should have been able to figure out myself if I'd thought about it a little more. :o) Great video!
Great tutorial hahaha you brought back the memories of formulas from school 35 years ago and i thought then I would never use them, my maths teacher would also like this. Perfection comes from precision measurements also saves u money throwing out trial & error mistakes. May the force be with you Jedi 😀😀😀
I would say for most applications if you are an experienced carpenter, you dont need the math. But in all honestly, the math makes it all the more beautiful :-)
@@OneTimeBuilds i hate math for not understanding. I LOVE math when i do get it. In this case, it takes a lot of guess work out. I’m still trying to debate what type of wood! 😆
First of all, congratulations on this video, it is very good and very well explained and detailed. I apologize if you don't understand me, I speak very bad English. I have a problem and I would like to know if you can help me. Using a saw blade has the problem of leaving gaps. My question is: Can the formula be modified to use a cone drill bit instead of a saw blade? example: at the extreme, the width of the groove is one millimeter and at 14 millimeters deep,the width of the groove is, for example, 2.5mm... How could I do the calculations? I have tried but I have not been able to do it correctly. Thank you so much.
You need to use the width of the gap at the surface. In a saw blade the width is more or less the same, in a cone cut the width will be biggest at the surface, so that should be your saw cut size. Hope it helps!
thanks for your answer. Unfortunately, with the cone drill bit it is different. although eliminating exactly the excess material R- and obtain the exact pieces, removing more from the other end, the final diameter is not what was expected. What I would like to know is if with the data I am going to give you you could do the exact calculations. For 180 degrees: R+ 10cm R- 7.4cm wood thickness 2.6cm 1mm conical router bit and the other end 4.5mm at 25mm depth. R+ = 6.28x100=628/2=314mm R- = 6.28x74=232.36/2=116.18mm R+ - R- = 197.82mm (198 material removed) 198mm/4.5mm router bit = 44 cuts 314-198=116mm/43 pieces=2.7mm Please where is the error and how can I fix it?
@@MiguelJimenezManzano ok.....the first error I see is that 6.28x74 is 464.....so half of that is 232.... but you are dividing by two again, which is wrong. Hope that helps.
Nice thing! Just division of the 110mm should be by 20 to get the spacing, because 19 cuts leave 20 uncut areas between the beginning and end-line. Kind of like cutting a bread: one piece --> 0 cuts ; two pieces --> 1cut; three pieces --> 2cuts ......
That's interesting. I was thinking that too but,,,, thinking of it as a clock face,,, with 60 segments and 60 markers on the outside (noting the curve is only on the outside, it's sixty straight lines on the inside) and let's say the circumference was exactly 60 cm\600mm to get a smooth looking curve you'd want 60 grooves cut at the centre of each minute section. For a ¼ circle you'd want 15 grooves but the the curve (the first groove) would actually start at 'half a minute' into the curve, the last would be 'half a minute' before the end. ! I got myself confused writing that but I think I understand it now! I hope you follow :) ____________________
;) btw and amazingly you don't need to calculate the internal and external circumferences. It's the thickness of the wood x2 ÷ 4(in this case of 90°*) x π * e.g. for 60° it'd be ÷ 6 12mm x 2 x π ÷ 4 ,,,,, 18.85 500 x 2 x π ÷ 4 ,,,,, 785.39 488 x 2 x π ÷ 4 ,,,,, 766.54 ,,,, difference 18.85 __________________ ;) Here's a great little bit of mental arithmetic if you want to have fun with somebody on a long car journey(and I had to have it explained to me,,, and I still wanted to see it on paper before I believed it) The earth's diameter is 12,000km There is a piece of rope tied right around it. The rope needs to be raised by ½ metre along its entire length. How much extra rope do you need to order?
I have done ply with the inside as the smooth side... but that bend makes the ply more likely to break. I suggest using steam or damp to facilitate the bend and the fill the outside gaps.
Sorry to comment on a 2-year old video, but I wanted to share my observation. I took this a step further and did this algebraically rather than numerical. The result is that the bend radius falls out of the equation. The number of kerfs is purely a function of bend angle, not the bend radius. So a 90deg cut needs 19-cuts, regardless of the bend radius. The bend radius defines the cut spacing. The equation is: A*R = A*(R-T) + n*K where A is your bend angle (in radians), R is your outer radius, T is your board thickness, n is the number of cuts and K is your blade kerf. Solve for n and you get: n=A*T/K In your example, with a 90deg bend (pi/2 radians), 12mm thick board, and a 1mm blade kerf, I get your 18.8 cuts like you did. FUN MATH! Seriously, thanks for the video. I nerded out pretty hard on this one.
Yes!! that is a great observation. A couple of comments below someone else wanted to bend in a cone shape and got indeed equal number of kerfs for both ends.
Thank you well explained ! Question if two different diameters one side R=124 angle 95° other side R=169 angle 116° , is this technique still possible by using fi the most cuts 25 (1mm saw) from the biggest dia. and/or should the cutting lines be parallel or angled to the smaller dia ? Thanks for help !
Hi, I fully understood the math you used and was able to confirm the results. I tried a larger radius of 203 mm using 12mm plywood . The calculations worked out to 19 cuts with a distance of 17 mm between cuts. I could not get the wood to bend and it kept snapping.
Thanks for making this video, I learned a lot! Any idea on the formula for making a bend that is at an angle other than 90°? If I wanted a 45° bend could I use a formula d=1/8*2*pi*r? I feel that I might be oversimplifying.
@@OneTimeBuilds Presently what we do now is make a rectangle shet a plywood with a mitre on one side Set the appropriate taper and cut all 8 sides assemble and re adjust the angle Simple it works but would be curious if there's a way to do it with math
Quick question/ thought: 19 cuts means 18 gaps between them. If you make the first and last cuts on the 110mm marks and divide the 110mm by 18 instead of 19, would this stil work?
Thanks for noticing! Other ppl also spotted the mistake. The introduced error with one extra or missing cut is however very small. Id say less than 5% which is probably lower than the overall error :-)
thnx i will try this... one more thing, i tried to find a staining video on your channel for all those colorful venears you have, but could not find one... i would love to learn how to make those as well... thnx again
Thanks for your tutorial, makes a whole lot of sense, and when one stops to think about the math involve, it makes even more sense. I have a little bit of a more challenging Kerfing project, where the bottom and the top of the curve that I need to achieve have a different radius. I am still bending the material one quarter turn (90 degrees), so when finished it will look like a quarter segment of a cone. The material thickness that I will be using is 19mm, the height will be 40cm. The bottom radius will be 20 cm and the top radius will be 10 cm. My initial thinking, without doing any background calculations, or trial and error experiments will be that the kerfing will have to be done at some corresponding angle. The other train of thinking will be that half the height of the kerfing will be calculated to meet the 20 cm radius while the other half will be calculated to meet the 10 cm radius. Your suggestion and thoughts on achieving this type of kerf bending will be greatly appreciated. Cheers
I have tried a cone shape bending before and your thinking is along the same lines. The biggest challenge is that the number of kerfs needs to be the same for both ends (because the kerfs need to meet) but the larger radius would need thicker kerfs. My cone kerf was not 100 percent successful though. Id say the best approach would be to calculate the kerfs needed for both, then use the result that gives the largest number of kerfs. You then space the marking of the kerfs on both ends and connect the lines, which will have a cone shape. Good luck with it!
@@OneTimeBuilds Again many thanks for your prompt reply. I like to show you the math, because for one reason or another even though the top and bottom radii are not the same, the amount of material that is required to be removed ended up being the same!! Known factors; material thickness 19mm Cone height 400mm Top radius. R. 100mm Small radius r. 81mm Bottom radius R. 200 mm Small radius. r. 181mm Saw blade thickness. 3mm Top kerfing calculations Big radius. 0.25X2X3.14X100=157- Small radius. 0.25X2x3.14X81=. 127 30mm 30mm, material to be removed at top radius Bottom kerfing calculations Big radius. 0.25X2X3.14xX200=314- Small radius. 0.25X2X3.24X181=. 284 30mm 30mm, material to be removed from bottom radius 30mm divide by 3mm (blade thickness)= 10 Need to cut 10 saw kerfs along top radius of 157mm and 10 saw kerfs along bottom radius of314mm Top radius 157 less 30=127 total space between kerfs, so 127 divided by 10=12.7 approx. spacing between kerfs at top radius Bottom radius 314 less 30=284 total space between kerfs, so divide 284 by 10= 28.4 approx. spacing between kerfs at bottom radius This is obvious that the kerfs will be at an angle Just have to come up will the formula to figure out the angle. Your input and/or review will be much appreciated Thanks
@@kathleenbonello679 it seems about right. No need for a formula for the angle, just connect kerf 1 top with 1 bottom, 2 top with 2 bottom etc. The cuts connect the marks at the top and the bottom.
@@kathleenbonello679 one more tip....the middle kerf will always be perpendicular to your top and bottom borders....so you use that one to draw and connect the rest so you dont need an angle
Hi Kurt! Thanks for your question. I try to cut in the middle, but I think cutting consistently in one side or the other will not make much of a difference.
Gerat Video! Thank you so much. I just wanted to ask you, what kind of saw do you use, or what do you recommend for this fine kerf? Thank you in advance!
Hi Attila, thanks for your comment. Im using a simple battery powered small circular saw. In particular Im using this model: www.praxis.nl/gereedschap-installatiemateriaal/elektrisch-gereedschap/zaagmachines/cirkelzagen/worx-handcirkelzaag-wx523-20v/5358900?channable=02490e696400353335383930307c&gclid=CjwKCAiAi_D_BRApEiwASslbJ2VPj_YTx9tdviHMJF2tdM6-J_BWoO4X4FygyCSoPjgeEi5YJMm70hoCacUQAvD_BwE
@@OneTimeBuilds This is awesome to! :) In case of cutting kerf on plywood I noticed that if we cut the wood more densely with a thin blade, the arc on the outer perimeter of the wood is much smoother. Not as square in outside as cutting with a wide blade.
Ok ... so I gotta ask. 5.8mm on a tape measure you can see the 5mm and you would have to guess at the .8 mm amount. On a table saw how do you continually adjust 5.8mm on each cut? What tools do you use? Do you use something like 321 blocks with feeler gauges?
@@OneTimeBuilds I guess my problem is that I'm not visualizing a solution. You have a strip of plywood x units in length. You have to slide said piece of wood down after each kerf. Which to me means that the space either left or right of the blade will get either larger or smaller meaning something has to move. Only thing that I could imagine is alike a finger joint jig where you slide the previously cut kerf onto some sort of reference point.
mmmm.... you can make a rig with kerfs of the right spacing... then you put the blade of the table saw in kerf 7 (or whatever number you are on) and fix the guide to the end of your rig. The next kerf, you use kerf 8 and repeat. The key of course is to build an accurate rig. You could also 3D print one with 20 kerfs or so :-)
Thank you for an amazing explanation! However, I find your handwriting very difficult to read. Without following your verbal dialogue I don’t think that I would be able to decipher it! As an example, some of your “mm abbreviations for millimetre” are simply a wavy line. Very informative nevertheless and I will be studying your video carefully as I need to kerf bend a perimeter curb for a custom lazy Susan that will be building. Thanks, John Jensen from British Columbia.
Would using an angled router/carving bit with a very narrow tip, say 6 degrees, 0.8 mm allow me to simply divide the degree of the bend by the angle of the bit, or would i not remove enough material? Thanks
Not too bad, but the calculation of how many kerfs(n) are required is much easier. The Outerradius (R) is only required to calculate the distance from kerf 1 to kerf n. R*π*a/180=(l) not required to calculate. Only following parameters are needed thickness of the wood (s), angle (a). The formula is: n=a*π*s/180 Distance(d) between kerfs i defined by d=l/n
Yes, you can simplify the formulas for a much faster calculation, but the point was to explain how to derive the formulas :-) not the final formula itself
This is fine teaching in action thank you! But I believe you made one error, and if not it would benefit me for you to correct me. When you divided outer radius (D)/ 19 wouldn’t that place the last kerf at the end of your radius? To contain all 19 kerfs evenly spaced would you not need 20 evenly spaced sections of remaining material? So wouldn’t the formula for spacing be D/(((D-d)/k)+1)
Yes...well spotted. I made the mistake but decided not to redo the entire video. The error is around 5% overall (1 over 20) and your blade and measuring is likely to introduce a larger error
I typically do around 90%, but it depends a bit on the material and how flexible it is. But generally, if the wood is 10mm thick, I would do 9mm cut and leave the last hardwood layer intact.
@@OneTimeBuilds From the way you do calculation you should be a mathematician bro. You make me remember the genius mathematician Leonhard Euler He used to wear hat as well . You must have something in common . Cheers ...:)
The first video I watched on this the guy grabbed his circular saw and free handed a bunch of random kerfs with the lumber over his knee. The result was remarkably similar.
You can totally wing it with a bit of experience.... but Im sucker for math and wanted to figure this out.....is it an overkill? .... yes....most likely it is.....is it beautiful and exact? .... yes....yes it is hahaha
Thanks! I always use standard wood glue and then fill the gaps (if any) with wood filler (or saw dust mixed with wood glue), but I guess expanding glue would do a good job also!
There's only one little problem in your calculations... 😁 If you have 19 grooves you will have 20 spaces in your specific distance.... 1 cut = 2 spaces, 2 cuts =3 equal spaces and so on... ☕from Italy 🙋🏻♂️ nice video and good explanation, by the way
@@OneTimeBuilds indeed, the error it's minor.. That wasn't my point 😁 you could get away with a 1 cut less or 1 more than the exact number.. Wood is very forgiving and flexible 😉 Especially if you wet the outside of the plywood in order to achieve a smooth bending, without any cracks or high spots (which happens when using a 4mm circular saw blade)
Very nicely done! 100 extra points for "Kerf bending is a pretty straight forward technique"
You are amazing Sir. You made it so easy. I am watching this for the second time from my saved videos. I just bought a circular saw and would like to try it out on a wider plywood
Great video Issac! Your explanation was so easy to follow and now I am armed with the information needed to tackle some new creations. Thank you so much!
Well done sir! I was searching for kerf cuts in metal for a welding project I am doing. There is not much information on YT on this subject but your video is such that I should be able to change values and make the cuts I need without any guesswork. This should help with my project immensely. Thank you for posting!
Awesome..I got tasked to build a crib for my great granddaughter...this is gonna get me there!!! GOD BLESS YOU SIR!
For those of us who never did well in math, this seems very complicated until you did such a beautiful job explaining each step. I'm looking at comments from others and getting myself more and more confused, so I'll slow down and take each comment into consideration when planning my cuts. Seems daunting, but I'm sure it's relatively easy as soon as you actually do it. Thanks!
Its not difficult once you understand the basic principle :-) and your bending will be very precise
I've been looking for this video for weeks! It finally really explained this concept to perfection.
Glad it was helpful!
What an amazing video! Ive been looking up kerf bending techniques and gotten a bit frustrated by how many people just have a kind of eye balling it approach to spacing the cuts, but i Love how it just makes so much SENSE the way you explained it! Thank you for this cool resource!
glad it was useful
And they said we would never use this type of math. Pfffft. You did a great job explaining everything. Just the kind of info and instruction was looking for. THANK YOU!
Im glad it was useful
I liked your video, and it made me think about something I really hadn't put much thought into before. I usually just cut a bunch of kerfs and move on, so thanks. If you want to greatly simplify your math... Circumference = C, radius = R, board thickness = T: C1 = 2piR1, C2 = 2piR2, R1 = R2 + T, C1 - C2 = 2piR1 - 2piR2 = 2pi(R2 + T) - 2piR2 = 2piR2 + 2piT - 2piR2 = 2piT
In other words, it doesn't matter the size of the circle, the difference in circumference between two circles that share the same center and are T thickness apart is always 2piT.
In your example of a 12mm board: 2 * 3.14 * 12mm = 75.36mm. We want a quarter of that for our 90deg bend. 75.36mm / 4 = 18.84mm --> your answer in the video.
For a 90deg bend, the answer will always be: (2piT)/4 = 0.5piT for a board thickness of T. A 180deg bend will be piT, and so on.
There is almost always an easier way. Most of the time, with some experience, just curring works fine. But the video was about exploring the exact way of doing it. Is it overkill? maybe yes hahaha
Nice, simple explanation.
One observation: Dividing 110 by 19, as you've done, means 19 grooves with 18 sections of 5.8mm between them, plus (half of) the two outer cuts, which comes to 105.4mm.
The remaining 4.6mm at the ends do not bend, they are part of the rest of the board which is straight, and this may be significant in some situations.
To have the last bend right at the end of the curve, you'll need to place the outermost grooves at the ends of the 110mm piece and divide the remainder by 18, i.e.: (110-2)/18=6mm.
Haha....yes....I realised this as I was editing the video. Good spot!
i was searchin the comment section just to see if someone else noticed😂
hahaha....yes yes...well spotted. The fact is that the difference with one groove will be negligible. It is only a 5% error when Im quite certain the error on my hand saw is higher :-)
@@OneTimeBuildswell it was no big misstake tho i was just curious n ur vid was actually really really helpful🙌
Hiya, I am having trouble understanding this. Could you possibly try and explain it better? "plus (half of) the two outer cuts, which comes to 105.4mm"- i dont quite understand this part and the last part. Thank you so much!
This is excellent!
My wife found a little bathroom trash can for $300 that I offered to make for her.
I wish I could get my hands on a CNC router to do the cuts accurately and fast.
Anyway, I really appreciate the math. Well done!
Brilliant!! This is information I have needed for some time now. So well explained!!!
Brilliant!!
My ADHD brain loved the math and application of your video!!
i was searching for calculations explained and thanks to this video it doesnt look so complicated anymore,great video and thanks again it helped alot ! :)
Im happy it was helpful
I really needed this.... You are a good master... thank you so much for you explanation .... Rodolfo Avila from Mexico City
Im glad it was useful Rodolfo
Thanks for the combination of skill ,sound, and art.
this is fantastic, have watched it several times now, and am planning to use this awesome in a project soooon ( my first small coffee table)
Glad you liked it!!
Good content in this video. Very logical! This will help me with the shop math. I need to make large round table skirt now I have the formula for success. Thanks!
I'm amazed that you traced and measured the final product on your tablet! It would never occur to me to do that instead of using paper and pencil. I am old fashioned. Great video!
Thanks for watching! I thought I would save 1 sheet of paper :-)
Your video is nicely done. The math is straight forward. The only thing missing is how deep should the cut be. I know there are zillion types of wood out there so it is nearly impossible to detail out. I guess I would have to try to cut pieces of wood that I normally work with, and do some trial and error to determine the depth of cut.
Many thanks for putting this video together.
That is indeed the one bit that highly depends on the type of wood. I typically use 80% to 90% of thickness of the wood as a reference.
cool - thank you :-) I have a little input on the bending..... before cutting the grooves, make sure that the growing lines of the wood in the last layer (the outer Parameter) are going with the bend ;-) thus the fibres can stretch. if the look across the bending, the wood will crack - oops built couple of drums and this was the first thing I learnt ;-) thougt it might help
Thanks for the tip...it totally makes sense!
Tnx note the math doesn't calculate the depht off the cut
I wasn't aware that the layers of ply stretch at all. However, now that I think about it, it makes total sense. Steam or hot water also works to avoid breaks. Also, I hear tell from someone who's done this for 50 years that adding liquid fabric softener (like for clothing) to the hot water makes bending even easier.
Thanks! I need to do some kerfing, and I've been looking at video after explanation after... and none of them
showed that it's actually a simple calculation that I should have been able to figure out myself if I'd thought about it a little more. :o) Great video!
Happy it was useful!
This video best explains it, been searching for it for days... Thank you
Im glad it was helpful!
You my friend are a bloody legend
Glad you liked it hahahaha
Great tutorial hahaha you brought back the memories of formulas from school 35 years ago and i thought then I would never use them, my maths teacher would also like this. Perfection comes from precision measurements also saves u money throwing out trial & error mistakes. May the force be with you Jedi 😀😀😀
hahaha....glad you enjoyed it!
Great video for dummies like me ,thanks bro.
Glad to help!
I’m torn between just doing it and being ocd with the math.
Thank you for doing the math 🥰
I would say for most applications if you are an experienced carpenter, you dont need the math. But in all honestly, the math makes it all the more beautiful :-)
@@OneTimeBuilds i hate math for not understanding. I LOVE math when i do get it. In this case, it takes a lot of guess work out. I’m still trying to debate what type of wood! 😆
First of all, congratulations on this video, it is very good and very well explained and detailed.
I apologize if you don't understand me, I speak very bad English.
I have a problem and I would like to know if you can help me.
Using a saw blade has the problem of leaving gaps.
My question is: Can the formula be modified to use a cone drill bit instead of a saw blade?
example: at the extreme, the width of the groove is one millimeter and at 14 millimeters deep,the width of the groove is, for example, 2.5mm...
How could I do the calculations?
I have tried but I have not been able to do it correctly.
Thank you so much.
You need to use the width of the gap at the surface. In a saw blade the width is more or less the same, in a cone cut the width will be biggest at the surface, so that should be your saw cut size. Hope it helps!
thanks for your answer. Unfortunately, with the cone drill bit it is different. although eliminating exactly the excess material R-
and obtain the exact pieces, removing more from the other end, the final diameter is not what was expected.
What I would like to know is if with the data I am going to give you you could do the exact calculations.
For 180 degrees:
R+ 10cm R- 7.4cm wood thickness 2.6cm
1mm conical router bit and the other end 4.5mm at 25mm depth.
R+ = 6.28x100=628/2=314mm
R- = 6.28x74=232.36/2=116.18mm
R+ - R- = 197.82mm (198 material removed)
198mm/4.5mm router bit = 44 cuts
314-198=116mm/43 pieces=2.7mm
Please where is the error and how can I fix it?
@@MiguelJimenezManzano Mmmm ....let me check it.... maybe it will be easier by email.
@@MiguelJimenezManzano ok.....the first error I see is that 6.28x74 is 464.....so half of that is 232.... but you are dividing by two again, which is wrong. Hope that helps.
Thank you sir, it helped me alot, ive been looking for this tecnique forever🙏🙏💐
Nice thing! Just division of the 110mm should be by 20 to get the spacing, because 19 cuts leave 20 uncut areas between the beginning and end-line. Kind of like cutting a bread: one piece --> 0 cuts ; two pieces --> 1cut; three pieces --> 2cuts ......
Good spot! two other people also spotted the error :-)
That's interesting.
I was thinking that too
but,,,,
thinking of it as a clock face,,, with 60 segments and 60 markers on the outside
(noting the curve is only on the outside, it's sixty straight lines on the inside)
and let's say the circumference was exactly 60 cm\600mm
to get a smooth looking curve you'd want 60 grooves
cut at the centre of each minute section.
For a ¼ circle you'd want 15 grooves
but the the curve (the first groove) would actually start at 'half a minute' into the curve, the last would be 'half a minute' before the end.
! I got myself confused writing that but I think I understand it now!
I hope you follow
:)
____________________
;) btw and amazingly
you don't need to calculate the internal and external circumferences.
It's the thickness of the wood x2 ÷ 4(in this case of 90°*) x π
* e.g. for 60° it'd be ÷ 6
12mm x 2 x π ÷ 4 ,,,,, 18.85
500 x 2 x π ÷ 4 ,,,,, 785.39
488 x 2 x π ÷ 4 ,,,,, 766.54 ,,,, difference 18.85
__________________
;) Here's a great little bit of mental arithmetic if you want to have fun with somebody on a long car journey(and I had to have it explained to me,,, and I still wanted to see it on paper before I believed it)
The earth's diameter is 12,000km
There is a piece of rope tied right around it.
The rope needs to be raised by ½ metre along its entire length.
How much extra rope do you need to order?
hahaha.....that is indeed a beautiful car journey challenge :-) The answer, I believe, is π meters.
Smashing lesson! Thanks very much! 👍
great video. one Q, i need to bend ply or MDF so that the smooth surface is on the inside, ie the concave side?
I have done ply with the inside as the smooth side... but that bend makes the ply more likely to break. I suggest using steam or damp to facilitate the bend and the fill the outside gaps.
@@OneTimeBuildsThanks for the idea. Its MDF and the radiuses vary, I will think about filling gaps too, it will require some experimenting (:👍
Hi,
Great, easy-to-understand video.
Nice video. I would have been nice to have your approach in algebra...
Thanks Steven!
15:42 The look you have when your work is verified accurate. haha. Puts a smile on your face!!
hahaha....it does....even when its only a bit of math and a piece of wood
Sorry to comment on a 2-year old video, but I wanted to share my observation. I took this a step further and did this algebraically rather than numerical. The result is that the bend radius falls out of the equation. The number of kerfs is purely a function of bend angle, not the bend radius. So a 90deg cut needs 19-cuts, regardless of the bend radius. The bend radius defines the cut spacing.
The equation is:
A*R = A*(R-T) + n*K
where A is your bend angle (in radians), R is your outer radius, T is your board thickness, n is the number of cuts and K is your blade kerf.
Solve for n and you get:
n=A*T/K
In your example, with a 90deg bend (pi/2 radians), 12mm thick board, and a 1mm blade kerf, I get your 18.8 cuts like you did.
FUN MATH! Seriously, thanks for the video. I nerded out pretty hard on this one.
Yes!! that is a great observation. A couple of comments below someone else wanted to bend in a cone shape and got indeed equal number of kerfs for both ends.
Thank you well explained ! Question if two different diameters one side R=124 angle 95° other side R=169 angle 116° , is this technique still possible by using fi the most cuts 25 (1mm saw) from the biggest dia. and/or should the cutting lines be parallel or angled to the smaller dia ? Thanks for help !
This video is sapping my will to live....and i love woodworking
Thats an easy fix....dont watch it!
Hi, I fully understood the math you used and was able to confirm the results. I tried a larger radius of 203 mm using 12mm plywood . The calculations worked out to 19 cuts with a distance of 17 mm between cuts. I could not get the wood to bend and it kept snapping.
I would suggest to cut less deep then. Depending on wood type, the stress of the bend might want to snap the wood.
Did you put HOT water with fabric softener in it? Soak it it with the hot water(spray bottle), wait a few and it should bend for you!
Metric is so beautiful, I dread doing this in imperial.
Thanks from Brazil. Excellent explanation 👏👏👏
Glad you liked it!
Thanks for making this video, I learned a lot! Any idea on the formula for making a bend that is at an angle other than 90°? If I wanted a 45° bend could I use a formula d=1/8*2*pi*r? I feel that I might be oversimplifying.
thank you sir. I was starting to try this, and now will use the math!!
You are welcome
Tapered endmills with a small tip radius will even give you a much better and stronger result.
Great video and easy to follow. Just one question can the same calculations work with MDF.
absolutely! the only key aspect is how deep the cut should be.
Este video es oro puro, gracias por el trabajo amigo.
De nada!
Very good explanation. Thank you
Awesome video, really helpful!
Im glad it was!
Very good tutorial and thanks for sharing this!
Glad it was helpful!
Brilliant explanation. Thank you!
Thank you!
Great explanation 👍
Nice job on the video have you ever thought about doing 1 on 4 sided compound mitres for columns
Thats an interesting idea!
@@OneTimeBuilds Presently what we do now is make a rectangle shet a plywood with a mitre on one side Set the appropriate taper and cut all 8 sides assemble and re adjust the angle Simple it works but would be curious if there's a way to do it with math
Great tutorial! You have a new sub! And the measurements are metric! Thanks again
Awesome, thank you! Glad you liked it!
can one do an asymmetrical bending? With different radius's on different ends?
I love you.. thaks for the explain. Hi feom Colombia
Glad it was useful!
Best explanation!! Thx!!
Quick question/ thought: 19 cuts means 18 gaps between them. If you make the first and last cuts on the 110mm marks and divide the 110mm by 18 instead of 19, would this stil work?
Thanks for noticing! Other ppl also spotted the mistake. The introduced error with one extra or missing cut is however very small. Id say less than 5% which is probably lower than the overall error :-)
Thank you, it was very helpful! What kind of glue do you recommend for the grooves?
I use regular wood glue....but I have seen people using expanding glue to fill the gaps
@@OneTimeBuilds Yeah, that’s why I asked. Thanks
My table saw kerf is 1/8 = about 4mm, how do I enter that on the calculation. Thanks
Awesome calculation ..
how deep do i need to cut? is this only for plywood, basically what type of wood would this work?
I would work on any wood. The depth of the cut depends on how hard the wood is. For plywood I cut 80 to 90 %.
thnx i will try this... one more thing, i tried to find a staining video on your channel for all those colorful venears you have, but could not find one... i would love to learn how to make those as well... thnx again
Thanks for your tutorial, makes a whole lot of sense, and when one stops to think about the math involve, it makes even more sense.
I have a little bit of a more challenging Kerfing project, where the bottom and the top of the curve that I need to achieve have a different radius. I am still bending the material one quarter turn (90 degrees), so when finished it will look like a quarter segment of a cone.
The material thickness that I will be using is 19mm, the height will be 40cm. The bottom radius will be 20 cm and the top radius will be 10 cm. My initial thinking, without doing any background calculations, or trial and error experiments will be that the kerfing will have to be done at some corresponding angle. The other train of thinking will be that half the height of the kerfing will be calculated to meet the 20 cm radius while the other half will be calculated to meet the 10 cm radius.
Your suggestion and thoughts on achieving this type of kerf bending will be greatly appreciated.
Cheers
I have tried a cone shape bending before and your thinking is along the same lines. The biggest challenge is that the number of kerfs needs to be the same for both ends (because the kerfs need to meet) but the larger radius would need thicker kerfs. My cone kerf was not 100 percent successful though. Id say the best approach would be to calculate the kerfs needed for both, then use the result that gives the largest number of kerfs. You then space the marking of the kerfs on both ends and connect the lines, which will have a cone shape. Good luck with it!
@@OneTimeBuilds Again many thanks for your prompt reply. I like to show you the math, because for one reason or another even though the top and bottom radii are not the same, the amount of material that is required to be removed ended up being the same!!
Known factors; material thickness 19mm
Cone height 400mm
Top radius. R. 100mm
Small radius r. 81mm
Bottom radius R. 200 mm
Small radius. r. 181mm
Saw blade thickness. 3mm
Top kerfing calculations
Big radius. 0.25X2X3.14X100=157-
Small radius. 0.25X2x3.14X81=. 127
30mm
30mm, material to be removed at top radius
Bottom kerfing calculations
Big radius. 0.25X2X3.14xX200=314-
Small radius. 0.25X2X3.24X181=. 284
30mm
30mm, material to be removed from bottom radius
30mm divide by 3mm (blade thickness)= 10
Need to cut 10 saw kerfs along top radius of 157mm and 10 saw kerfs along bottom radius of314mm
Top radius 157 less 30=127 total space between kerfs, so 127 divided by 10=12.7 approx. spacing between kerfs at top radius
Bottom radius 314 less 30=284 total space between kerfs, so divide 284 by 10= 28.4 approx. spacing between kerfs at bottom radius
This is obvious that the kerfs will be at an angle
Just have to come up will the formula to figure out the angle.
Your input and/or review will be much appreciated
Thanks
@@kathleenbonello679 it seems about right. No need for a formula for the angle, just connect kerf 1 top with 1 bottom, 2 top with 2 bottom etc. The cuts connect the marks at the top and the bottom.
@@kathleenbonello679 one more tip....the middle kerf will always be perpendicular to your top and bottom borders....so you use that one to draw and connect the rest so you dont need an angle
@@OneTimeBuilds Thanks for your input. Looking forward to actually trying on some material, but it won’t be for a couple of weeks
Hey my friend r we cutting our grooves on the centerline of each mark or right or left of the mark? Thanks.
Hi Kurt! Thanks for your question. I try to cut in the middle, but I think cutting consistently in one side or the other will not make much of a difference.
Gerat Video! Thank you so much. I just wanted to ask you, what kind of saw do you use, or what do you recommend for this fine kerf? Thank you in advance!
Hi Attila, thanks for your comment. Im using a simple battery powered small circular saw. In particular Im using this model: www.praxis.nl/gereedschap-installatiemateriaal/elektrisch-gereedschap/zaagmachines/cirkelzagen/worx-handcirkelzaag-wx523-20v/5358900?channable=02490e696400353335383930307c&gclid=CjwKCAiAi_D_BRApEiwASslbJ2VPj_YTx9tdviHMJF2tdM6-J_BWoO4X4FygyCSoPjgeEi5YJMm70hoCacUQAvD_BwE
@@OneTimeBuilds Thank you so much for your kind help. :) this is the best kerf calculating video. Do more :) Regards from Budapest!
Thank you! I made another similar one on calculating angles for joining boards :-) ua-cam.com/video/ZYAxcUHvQUQ/v-deo.html
@@OneTimeBuilds This is awesome to! :) In case of cutting kerf on plywood I noticed that if we cut the wood more densely with a thin blade, the arc on the outer perimeter of the wood is much smoother. Not as square in outside as cutting with a wide blade.
@@attilasipeki1418 Yes, that is absolutely true! The thinner the blade, the smoother the curve!
What if I say I'm gonna cut it with table saw blade 3mm instead of 1mm handsaw. How many grooves gonna cut??
will this work with solid wood?
yes it will. The thing to consider is how deep to cut depending on the stiffness of the wood
Ok ... so I gotta ask. 5.8mm on a tape measure you can see the 5mm and you would have to guess at the .8 mm amount.
On a table saw how do you continually adjust 5.8mm on each cut? What tools do you use? Do you use something like 321 blocks with feeler gauges?
I guess on a table saw you can make a rig that is exactly 5.8 and use it as reference
@@OneTimeBuilds
I guess my problem is that I'm not visualizing a solution. You have a strip of plywood x units in length. You have to slide said piece of wood down after each kerf. Which to me means that the space either left or right of the blade will get either larger or smaller meaning something has to move. Only thing that I could imagine is alike a finger joint jig where you slide the previously cut kerf onto some sort of reference point.
mmmm.... you can make a rig with kerfs of the right spacing... then you put the blade of the table saw in kerf 7 (or whatever number you are on) and fix the guide to the end of your rig. The next kerf, you use kerf 8 and repeat. The key of course is to build an accurate rig. You could also 3D print one with 20 kerfs or so :-)
Thank you for an amazing explanation! However, I find your handwriting very difficult to read. Without following your verbal dialogue I don’t think that I would be able to decipher it! As an example, some of your “mm abbreviations for millimetre” are simply a wavy line. Very informative nevertheless and I will be studying your video carefully as I need to kerf bend a perimeter curb for a custom lazy Susan that will be building.
Thanks, John Jensen from British Columbia.
How do we know what our big R measurement is?
That is the outside radius of your piece
Thank you 🙏🙏🙏
You are welcome
Thankyou - saved much guessing
I am excellent with spread sheets so i will make a spread sheet with all the formulas
Excellent, perfect, thanks' a lot !
This is soooooo helpful! Thank you!
Thank you....glad it was.
Great explanation
Glad you liked it!
Would using an angled router/carving bit with a very narrow tip, say 6 degrees, 0.8 mm allow me to simply divide the degree of the bend by the angle of the bit, or would i not remove enough material? Thanks
I dont think so. The issue is not the angle but the length of the material that jas to be removed
Thank you. I just did a bend but I wish I would have watched this first!
hahaha....you always learn something new!
This help me a lot. Thx Bro.
Perfect. Thanks
Thank You!
Мужик, огромное тебе спасибо!😀
You are welcome.
Hello, can you please tell us what wood material is that what you showed so flexible ?
Plywood :-)
@@OneTimeBuilds Thank you, but i want to know if is pine, oak, ? Thank you
ahh!!! it is Birch. It is a very common material in The Netherlands. Hope that helps!
Friendly and simple : thank you !
You're welcome!
Not too bad, but the calculation of how many kerfs(n) are required is much easier.
The Outerradius (R) is only required to calculate the distance from kerf 1 to kerf n.
R*π*a/180=(l)
not required to calculate. Only following parameters are needed thickness of the wood (s), angle (a).
The formula is: n=a*π*s/180
Distance(d) between kerfs i defined by d=l/n
Yes, you can simplify the formulas for a much faster calculation, but the point was to explain how to derive the formulas :-) not the final formula itself
This is fine teaching in action thank you! But I believe you made one error, and if not it would benefit me for you to correct me. When you divided outer radius (D)/ 19 wouldn’t that place the last kerf at the end of your radius? To contain all 19 kerfs evenly spaced would you not need 20 evenly spaced sections of remaining material? So wouldn’t the formula for spacing be D/(((D-d)/k)+1)
Yes...well spotted. I made the mistake but decided not to redo the entire video. The error is around 5% overall (1 over 20) and your blade and measuring is likely to introduce a larger error
Magnifique !!!
Can we curve it till its become circular?
Absolutely! There will be some limits based on the wood and radius, but it can be done.
Or depending what your making,just make it oversized and cut it exactly to size.
Thank you! It’s thats what I needed
Thanks from Turkey.
Welcome and I hope it was helpful!
How deep did you make the cuts with your circular saw?
I typically do around 90%, but it depends a bit on the material and how flexible it is. But generally, if the wood is 10mm thick, I would do 9mm cut and leave the last hardwood layer intact.
@@OneTimeBuilds thank you so very much. Great tutorial
@@MrBrewsk Great that it was helpful!
I this this is a great explanation, however, if I subtract 81.1 from 109.9 I get 28.8. Did I miss something?
It is 91.1 :-) Sorry about my horrible hand writing.
@@OneTimeBuilds got it
That yellow hat help with the calculation?
It is a very important component XD
@@OneTimeBuilds From the way you do calculation you should be a mathematician bro.
You make me remember the genius mathematician Leonhard Euler
He used to wear hat as well .
You must have something in common .
Cheers ...:)
Thank you so much for this video
The first video I watched on this the guy grabbed his circular saw and free handed a bunch of random kerfs with the lumber over his knee. The result was remarkably similar.
You can totally wing it with a bit of experience.... but Im sucker for math and wanted to figure this out.....is it an overkill? .... yes....most likely it is.....is it beautiful and exact? .... yes....yes it is hahaha
Just for people that may not know and see it somewhere else... the perimeter, as he is calling it, is known as the circumference
Yes! the circumference of a circle is also its perimeter hahaha Thanks for pointing this out!
Excellent explanation!
Just a single doubt: the glue can be vinilic or poliurethanic expanding type? Thanks a lot for your time! Néstor.
Thanks! I always use standard wood glue and then fill the gaps (if any) with wood filler (or saw dust mixed with wood glue), but I guess expanding glue would do a good job also!
Extremely usefull, thanks
Glad to hear that!
There's only one little problem in your calculations... 😁 If you have 19 grooves you will have 20 spaces in your specific distance.... 1 cut = 2 spaces, 2 cuts =3 equal spaces and so on... ☕from Italy 🙋🏻♂️ nice video and good explanation, by the way
Yes....I made that mistake and someone spotted a few hundred comments below. Good catch. Overall however, 1 space in 20 is only a 5% error :-)
@@OneTimeBuilds indeed, the error it's minor.. That wasn't my point 😁 you could get away with a 1 cut less or 1 more than the exact number.. Wood is very forgiving and flexible 😉 Especially if you wet the outside of the plywood in order to achieve a smooth bending, without any cracks or high spots (which happens when using a 4mm circular saw blade)
@@_777Z Yes....you are totally right!
Wow! That was a fabulous explanation! Thank you very much!
You are welcome!
Very very interesting!!!!
Thank you!