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.
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)
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.
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.
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.
Keep in mind that as the pressure cone widens the actual pressure on the joint weakens dramatically. So your 400 psi clamp delivers nowhere near 400 psi in the actual join unless it`s edge banding. There is pretty much no way to over clam a join and squeeze all the glue out. Try it.
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.
Disappointed that there was no mention of band clamps. I know a good 90% of them are used for corner clamping, but I don't see why one couldn't make additional bits to add parallel portions to the band. I know the original study probably didn't include them, because they're honestly significantly different from every other clamp, which are all relatively the same in their basic function. It'd be nice to see a study done on band style clamps, as one would think a taut band would provide the same amount of clamping pressure along the band, yet I have a feeling the central portion of a band, especially along a long surface, would have more give than it would in the corners.
I'm in the market for some new clamps but there's no stock of the type I want due to corona virus. This virus has got to be stopped! I need new clamps.
Someone like me can probably get 2 million psi out of an F style clamp. Sounds like this needs to be a competition. Crafted Workshop, April Wilkerson, FTBT, John Malecki, and JKM compete for charity.
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 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.
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
Links, Formula and Types of Wood PSI Needed Below: *Support What We Do at The Katz-Moses Store* bit.ly/KMWstore20 *Clamps Main Page( qty discounts are big fyi):* lddy.no/m61p *Parallel Clamps:* lddy.no/m61q *F-StyleClamps (bar clamps):* lddy.no/m61s *Pipe Clamps:* lddy.no/m61u *Bottom Line: Use More Than You Need. Don’t Get Hung Up On Trying to Calculate to Use the Least Amount. More Clamps, Less Stress* *Formula:* (Glue Surface Area X PSI Needed) / Clamp PSI = Clamps Needed (Then Divide By Length of Clamping Pressure at Glue Line) ¼ Sawn First # in PSI and Flat Sawn 2nd # in PSI Pine: 150 , 300 Cherry: 250, 500 Walnut: 300, 600 Oak: 450,900 Maple: 600, 1200 Link to Roman Rabiej’s Paper www.semanticscholar.org/paper/The-Effect-of-Clamping-Pressure-and-Orthotropic-on-Rabiej-Behm/d417c31a096c58592273f25683b95ddad48c1aaf Fine Woodworking Article by Roman Rabiej: www.finewoodworking.com/2007/11/01/get-serious-about-clamping
@@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!"
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 do enjoy and watch your videos but you interchanged psi and pounds incorrectly at times which was confusing. Dont freak out everyone...I gave him a "like". Units are important.
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.
1,200psi for Maple??? Highly doubtful. "Dale Zimmerman of Franklin International, maker of Titebond woodworking glues, recommends 100 to 150 pounds per square inch (psi) for clamping softwoods and 175-250 psi for hardwoods." I think that the people that make wood glues and do exhaustive destructive testing of likely thousands of wood glue joints on lots of wood varieties know the proper amount of pressure required.
I would like to see this revisited; I would like to see if your clamp recommendations have changed over time. Also nice to fix your math issues (it is very distracting for a picky person).
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...
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.
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?
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.
How many clamps do i need for a 2 inch long board? Hold on while I grab my TI83 calculator, and I'll tell you. Okay you need 2.3457 clamps cubed. Seriously tho nice video. Always good to see some real data instead of just winging it.
I’m pretty sure that your analysis here violates Newton’s 2nd law. If you have 400 pounds of force from the clamp over 1 square inch at the surface, if you now assume that clamping force is being spread over 8 square inches at the joint, you now have 50 psi at the joint. This analysis assumes that by putting 400 pounds of force on the clamp, that the force exerted will increase until you reach the maximum at the joint. In other words, a violation of conservation of momentum.
Hmm well it seems the Taylor parallel clamps are sold in 4 packs with 2 x 24 and 2 x 36 for about $190 on their site. Now the bessey framing kit with also 4 clamps is offered at the Depot for $199 right now so frankly I'd go with the Bessey. The reason the Besseys are not as smooth is because once you set a distance you can put the clamps vertically and the adjustable part of the clamp will stay in place unaffected by gravity. It's a bit of a tradeoff. Good deal at the depot. That's a new lower price so not even a sale. Mind you I think the Besseys are mostly made in China now so hard to find those made in Germany versions these days
I don't think your math is correct. You are mixing pressure and force. It should be Glue Force = Area of Wood * PSI of species: the result of this is a force. Next, divide by the force of each clamp to get a unitless number which represents the number of clamps. You are dividing the glue force by pressure which leaves you with a unit of sq. inches which is not unitless and an indication of an error in the formula. Otherwise good video. I like that you are trying to explain this topic.
Sorry Jonathan. I love your content, but you butchered this video. I wish I could find the source material you reference, but I did some searching and came up blank. The good news is that this doesn't really matter. Thermoplastic glues like PVA aren't structural, so it doesn't make much sense to worry this much about it. Their strength is way too variable with conditions over time to be reliable for anything important. The reason researchers study adhesive joint strength is for structural applications. If a manufacturer uses a thermoset glue to make a glulam beam, they need the glue joints to be strong, uniform, and predictable. Woodworkers don't really need that. We design our joinery to bear the loads and the glues simply hold the joints together. I think the 45 degree rule of thumb to achieve a unifirm glue-up is reasonable, but don't take it too seriously. If your glue joints don't fall apart and look good, you're doing it right.
I don't see the 45 degree business like you do. You seem to believe that the force is uniform across that 45 degree cone. I believe it is a vector force that varies with the sine of the angle. But let's do a "thought experiment": You take a pair of 8 inch boards, 16 inches long, and you go to glue them together. Using the 45 degree rule, you could clamp them together with one clamp in the center (assuming you could generate enough pressure, which I believe easy for the right woods/grains). Do you imagine that the force out at the outside of the glue joint is sufficient to push them together much? Do you think that a slight imperfection that would be easily overcome in the center would likewise be handled out at the edge? No, we all know that would not be the case and we all would put clamps closer to the edge; perhaps only 2 clamps, but definitely positioned so they are applying their force more perpendicular to the glue joint.
Thanks so much for the knowledge that you share for free... I'm from Chile... may you please speak a little bit slower??? I apoligize for my poor english level...
I know its been a couple years for this video, but the moment you lost me was when you claimed that a squeeze clamp can apply the same amount of force as a standard F-clamp. Anyone that thinks they are enough for a glue up is kidding themselves. The only way that would be likely is if you had them butted up to each other side by side the whole length of the glue line, then they "Might" be applying enough force for a reasonable glue up
You clearly don't understand the physics or the units involved. The math is gibberish. Force (lbs) and pressure (psi) are different units; one is absolute, the other is normalized by area. You're not helping anyone with this nonsense
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
So if it’s true in the example you discussed that the formula stated that 47 clamps are needed and nobody does that then either we should see evidence of widespread joint failures or the research results are incorrect. I wonder how the researcher came up with his required PSI values. I guess I’ll just try to space clamps at 2x the board width or less and crank them as hard as I can.
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.
this calculating is boring just put as much clams on u can and u shuld be good work for me every time when im gluing table top i glue 3 pice off board at time and then i combine all in one most off time i dont need to plane flat just sanding and its done
Your calculations are flawed not all the conditions are accounted for such as distance from load and compression of wood fibers at load points and other factors.
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.
My one complaint about clamping pressure info is the whole “PSI” thing. Of course, I COMPLETELY understand that a measurement like PSI is the only way to be able to properly quantify/calculate such things...but what human has any sense for a measurement like PSI? Atmospheric pressure, tire pressure, clamping force, animal bite force...all things that people will give you “PSI” for but honestly, on a human level, what is a pound per square inch? What does that feel like? What kind of force do you need to apply with your hands in order to achieve 10 PSI within a joint, etc? It’s just not a very human experience. If someone related that to “yeah, such and such psi is like a large textbook resting on your balls”, at least THAT would give you some sense of the force involved.
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.
The old bessey F clamps I had were rubbish. They would release on mass if the project was bumped. The newer F clamps with the clutch plates work well and do not release when subject to vibration. I almost feel guilty about the older Bessy clamps, I gave around 4 dozen away to people who were always the first to make sure they did not miss out on anything going for free, I hope they experience the same level of frustration I did. I don't like grasping people. All the best.
ha man I really enjoy your videos and wealth of knowledge. However you need to switch to decaf before you do your videos. You speak at the rate of a auctioneer, which makes following your thought process a little difficult.
Really, three things.. 1. what are friends for if not to make fun of online 2. After this video the only call I am going to use is the one to you to come clamp my stuff up 3. Since when was the pathagaJIM formula easy.... LOL
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?
@ 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.
![DDG & G Herbo - Nosey [Official Video]](http://i.ytimg.com/vi/I9Ra0Zc2NlQ/mqdefault.jpg)
Adding a little paste wax to parallel clamp bars completely solves the difficulty opening/closing em. and it stops glue from sticking to em.
Great information. When I started woodworking I was constantly over tightening and it absolutely makes the joint less strong.
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.
Thanks for sharing
This guy is the woodworking sensei
Mc Katz-Moses dropping them bars at 16:37
"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 ruclips.net/channel/UCievvwx_-UU-rP28103rUCw
What I was wondering after this. is what about say a butcher block? multiple seams?
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.
Taytools appears to no longer have parallel clamps unfortunately. Still loving yours? Might hold out in case they come back in stock!
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.
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.
Poor Will Walker. LOL
Keep in mind that as the pressure cone widens the actual pressure on the joint weakens dramatically. So your 400 psi clamp delivers nowhere near 400 psi in the actual join unless it`s edge banding. There is pretty much no way to over clam a join and squeeze all the glue out. Try it.
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.
Where did you get your marking knife from Jonathan?
WD-40 on those parallel clamps!!
OH... the William Walker slam.... Is he still alive? Haven't seen much content lately.
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
Disappointed that there was no mention of band clamps. I know a good 90% of them are used for corner clamping, but I don't see why one couldn't make additional bits to add parallel portions to the band.
I know the original study probably didn't include them, because they're honestly significantly different from every other clamp, which are all relatively the same in their basic function. It'd be nice to see a study done on band style clamps, as one would think a taut band would provide the same amount of clamping pressure along the band, yet I have a feeling the central portion of a band, especially along a long surface, would have more give than it would in the corners.
Can you explain where is that 45 degree info coming from?
I'm in the market for some new clamps but there's no stock of the type I want due to corona virus. This virus has got to be stopped! I need new clamps.
Click the links in the pinned comment. Tons of my favorites available
Hope there available in the UK cheers.
They ship internationally. Not sure the cost but they're 37% cheaper than jet and bessey
Someone like me can probably get 2 million psi out of an F style clamp. Sounds like this needs to be a competition. Crafted Workshop, April Wilkerson, FTBT, John Malecki, and JKM compete for charity.
Malecki would win that for sure
Please stop with the Taytools sales add.
Jimmy kimmel...??
“...let’s talk about how pressure is allocated...” - I need you to talk to my boss....
For a minute there I thought that you were trying to convince me that I have enough clamps...
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 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.
So...halfway through I questioned whether or not I’m smart enough to be a woodworker. I’m sticking with, “A lot and tight.”
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.
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
Links, Formula and Types of Wood PSI Needed Below:
*Support What We Do at The Katz-Moses Store* bit.ly/KMWstore20
*Clamps Main Page( qty discounts are big fyi):* lddy.no/m61p
*Parallel Clamps:* lddy.no/m61q
*F-StyleClamps (bar clamps):* lddy.no/m61s
*Pipe Clamps:* lddy.no/m61u
*Bottom Line: Use More Than You Need. Don’t Get Hung Up On Trying to Calculate to Use the Least Amount. More Clamps, Less Stress*
*Formula:*
(Glue Surface Area X PSI Needed) / Clamp PSI = Clamps Needed (Then Divide By Length of Clamping Pressure at Glue Line)
¼ Sawn First # in PSI and Flat Sawn 2nd # in PSI
Pine: 150 , 300
Cherry: 250, 500
Walnut: 300, 600
Oak: 450,900
Maple: 600, 1200
Link to Roman Rabiej’s Paper www.semanticscholar.org/paper/The-Effect-of-Clamping-Pressure-and-Orthotropic-on-Rabiej-Behm/d417c31a096c58592273f25683b95ddad48c1aaf
Fine Woodworking Article by Roman Rabiej: www.finewoodworking.com/2007/11/01/get-serious-about-clamping
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.
You are quickly becoming my favorite woodworking RUclipsr. I love your style and the way you talk through things. Thanks for being you! ^_^
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.
You're giving Will about 4 more psi than I would. Great stuff, bro!
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!
I do enjoy and watch your videos but you interchanged psi and pounds incorrectly at times which was confusing. Dont freak out everyone...I gave him a "like". Units are important.
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!
bullshit those quick clamps apply that much pressure
@ 1:34 .... BLASPHEMER!!!!!!!!!!!!!!!!!!!!!! 1500 tons per sq/mm is adequate for ⅛" thick MDF laminate!!!! Lol
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” 😂
🤣🤣
1,200psi for Maple??? Highly doubtful. "Dale Zimmerman of Franklin International, maker of Titebond woodworking glues, recommends 100 to 150 pounds per square inch (psi) for clamping softwoods and 175-250 psi for hardwoods." I think that the people that make wood glues and do exhaustive destructive testing of likely thousands of wood glue joints on lots of wood varieties know the proper amount of pressure required.
I would like to see this revisited; I would like to see if your clamp recommendations have changed over time. Also nice to fix your math issues (it is very distracting for a picky person).
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...
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 just put on the clamps😈😈😈
Ouch, remind me not to get into a spat with you (or even get into a friendly tit-for-tat). William Walker, looking for your reply!
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?
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.
How many clamps do i need for a 2 inch long board? Hold on while I grab my TI83 calculator, and I'll tell you. Okay you need 2.3457 clamps cubed.
Seriously tho nice video. Always good to see some real data instead of just winging it.
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
I’m pretty sure that your analysis here violates Newton’s 2nd law. If you have 400 pounds of force from the clamp over 1 square inch at the surface, if you now assume that clamping force is being spread over 8 square inches at the joint, you now have 50 psi at the joint. This analysis assumes that by putting 400 pounds of force on the clamp, that the force exerted will increase until you reach the maximum at the joint. In other words, a violation of conservation of momentum.
Hmm well it seems the Taylor parallel clamps are sold in 4 packs with 2 x 24 and 2 x 36 for about $190 on their site. Now the bessey framing kit with also 4 clamps is offered at the Depot for $199 right now so frankly I'd go with the Bessey. The reason the Besseys are not as smooth is because once you set a distance you can put the clamps vertically and the adjustable part of the clamp will stay in place unaffected by gravity. It's a bit of a tradeoff. Good deal at the depot. That's a new lower price so not even a sale. Mind you I think the Besseys are mostly made in China now so hard to find those made in Germany versions these days
I don't think your math is correct. You are mixing pressure and force. It should be Glue Force = Area of Wood * PSI of species: the result of this is a force. Next, divide by the force of each clamp to get a unitless number which represents the number of clamps. You are dividing the glue force by pressure which leaves you with a unit of sq. inches which is not unitless and an indication of an error in the formula. Otherwise good video. I like that you are trying to explain this topic.
Sorry Jonathan. I love your content, but you butchered this video. I wish I could find the source material you reference, but I did some searching and came up blank. The good news is that this doesn't really matter. Thermoplastic glues like PVA aren't structural, so it doesn't make much sense to worry this much about it. Their strength is way too variable with conditions over time to be reliable for anything important.
The reason researchers study adhesive joint strength is for structural applications. If a manufacturer uses a thermoset glue to make a glulam beam, they need the glue joints to be strong, uniform, and predictable. Woodworkers don't really need that. We design our joinery to bear the loads and the glues simply hold the joints together. I think the 45 degree rule of thumb to achieve a unifirm glue-up is reasonable, but don't take it too seriously. If your glue joints don't fall apart and look good, you're doing it right.
I don't see the 45 degree business like you do. You seem to believe that the force is uniform across that 45 degree cone. I believe it is a vector force that varies with the sine of the angle. But let's do a "thought experiment": You take a pair of 8 inch boards, 16 inches long, and you go to glue them together. Using the 45 degree rule, you could clamp them together with one clamp in the center (assuming you could generate enough pressure, which I believe easy for the right woods/grains). Do you imagine that the force out at the outside of the glue joint is sufficient to push them together much? Do you think that a slight imperfection that would be easily overcome in the center would likewise be handled out at the edge? No, we all know that would not be the case and we all would put clamps closer to the edge; perhaps only 2 clamps, but definitely positioned so they are applying their force more perpendicular to the glue joint.
Thanks so much for the knowledge that you share for free... I'm from Chile... may you please speak a little bit slower??? I apoligize for my poor english level...
I know its been a couple years for this video, but the moment you lost me was when you claimed that a squeeze clamp can apply the same amount of force as a standard F-clamp.
Anyone that thinks they are enough for a glue up is kidding themselves. The only way that would be likely is if you had them butted up to each other side by side the whole length of the glue line, then they "Might" be applying enough force for a reasonable glue up
You clearly don't understand the physics or the units involved. The math is gibberish. Force (lbs) and pressure (psi) are different units; one is absolute, the other is normalized by area. You're not helping anyone with this nonsense
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
So if it’s true in the example you discussed that the formula stated that 47 clamps are needed and nobody does that then either we should see evidence of widespread joint failures or the research results are incorrect. I wonder how the researcher came up with his required PSI values. I guess I’ll just try to space clamps at 2x the board width or less and crank them as hard as I can.
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.
15:15, What kind of math are you talking about? Lol. You don't get more psi over bigger distance.
Not going to lie, I always crank em' down. Never thought to sit and so the math on that. Good video. Thank you, Johnathan! :)
Another great video. Love your channel Jonathan. Ps f_ _ k William walker. Power to the Moses.
Another fact about pipe clamps, they make you see stars when one falls on your head! Don’t ask me how I know. It still hurts to think about it.
“I can bend that with just my hands” well, sure JKM can bend it, but I bet William walker couldn’t bend that clamp.
That's all well and good, but how about the pressure / force for veneering? o.O
this calculating is boring just put as much clams on u can and u shuld be good work for me every time
when im gluing table top i glue 3 pice off board at time and then i combine all in one most off time i dont need to plane flat just sanding and its done
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 👍
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!
Why are those Kreg Specialty clamps so expensive. Man $40 apiece?
Your calculations are flawed not all the conditions are accounted for such as distance from load and compression of wood fibers at load points and other factors.
How do you know the PSI needed depending on tree type? Is there a source somewhere I can find this info?
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.
anybody know where to source the heavier duty f clamps?
Fantastic tips, Jonathan! Thanks a lot!!! 😃
Stay safe there with your family! 🖖😊
It's nice to know all that, but we build furniture, not rockets.
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!
Watching this video stressed me out. Too much pressure.
Clamps?... Clamps??? CLAAAMPS!!??.. CLAAAAMPS!!!!!??
CLAAAAMPS??????
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
I always enjoy your videos. Just wish there was a double-like button.
My one complaint about clamping pressure info is the whole “PSI” thing. Of course, I COMPLETELY understand that a measurement like PSI is the only way to be able to properly quantify/calculate such things...but what human has any sense for a measurement like PSI? Atmospheric pressure, tire pressure, clamping force, animal bite force...all things that people will give you “PSI” for but honestly, on a human level, what is a pound per square inch? What does that feel like? What kind of force do you need to apply with your hands in order to achieve 10 PSI within a joint, etc? It’s just not a very human experience. If someone related that to “yeah, such and such psi is like a large textbook resting on your balls”, at least THAT would give you some sense of the force involved.
Bessey is upset you called their clamps a Pony
You had me at "squishy meatbags"
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.
I would've never imagined that Jimmy Kimmel had such extensive woodworking knowledge.
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.
The old bessey F clamps I had were rubbish. They would release on mass if the project was bumped. The newer F clamps with the clutch plates work well and do not release when subject to vibration. I almost feel guilty about the older Bessy clamps, I gave around 4 dozen away to people who were always the first to make sure they did not miss out on anything going for free, I hope they experience the same level of frustration I did. I don't like grasping people. All the best.
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?
ha man I really enjoy your videos and wealth of knowledge. However you need to switch to decaf before you do your videos. You speak at the rate of a auctioneer, which makes following your thought process a little difficult.
Usually I really like your videos, but this one is needlessly complicated. And you've got force and pressure mixed up.
Really, three things.. 1. what are friends for if not to make fun of online 2. After this video the only call I am going to use is the one to you to come clamp my stuff up 3. Since when was the pathagaJIM formula easy.... LOL
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?
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?
@ 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.
As clamps don't come with a PSI gauge there is no way of telling how much pressure you are applying, so it comes down to your own grip.