New Bessey K Body Revo - added force?

[Will Blick]

Just got my first K Body Revo's. Bessey touts:

REVO™ design exerts 25% more clamping force than original K Body®

I tested the Revos against the standard K Bodies with a pressure gauge.... and the ol K bodies slightly out performed the new Revos. About 800 lbs of force with a good grip... maybe 20lbs less with the new Revo. I oiled the Revos up, but to no avail.

Bessey had a great opportunity on this clamp to allow the handle to swivel 90 deg. to gain the added force, and reduce skin blisters, but I guess cost prevented such.

While the new Revo has some slightly better build issues, IMO, the old K bodies are quite the bargain while they still last.

[Jason Beam]

I wondered about that claim, myself. Can you inspect the thread on the two and see if they're at all different? If they didn't change the thread, there's no real logic to their claim. But if they messed with the pitch on that lead screw, they might have a mathematical increase - something they can prove on paper, i guess.

I like my good ole' standard besseys, myself. :)

[Will Blick]

Can't see any difference in the threads...... I think the claim for greater force came as a result of the synthetic grip..... the problem is, its still close to being round and not much thicker than the wood K body grips..... so no great improvement IMO.

OTOH, the Stanley Bailey's have a super thick grip, in triangular shape.... I can easily drive them to 1100 lbs without ripping my hands apart.... Stanley got the grip right...the entire Baily clamp is VERY impressive.... I bought some 12"'s.... but for longer, I still like the flexibility of the K's, as I can link them together... as well as the Jets.

[Brent Smith]

Hi Will,

I've been wondering about that claim of more clamping power, specifically why was it added (which apparently it was not). as I see it the old K-Bodies have more than enough. If you need to clamp down any harder than that, there's a problem with your joint.

[Anthony Anderson]

as I see it the old K-Bodies have more than enough. If you need to clamp down any harder than that, there's a problem with your joint.

That is what I was thinking Brent. Just like you said, if the joint is prepared properly, then such excessive force will only starve the glue joint. Was also wondering if the Revo clamps had a head that adjusts for angles. I thought I saw that somewhere. Bill

BTW, I really like my original K-Bodys.

[Will Blick]

More bad news... Revo after 30 minutes lost 200 lbs of pressure. Only my bar clamps slip this bad.... maybe because its new, so I will give it time, but not a good sign. Slippage is one of the most overlooked aspects of clamps. Only a gauge will advise you, it's deceiving. Again, the Stanlyes are the best in this category also, after 30 minutes, they barely loose 50 lbs on avg, and considering they are starting at over 1000 lbs of force, quite impressive. As I have mentioned before, I find it amazing that Stanley entered the clamp game so late, and yet, made a killer parallel clamp.


I hate to turn this thread into a "how much pressure" thread. But in short,


1) its almost impossible to starve a joint of glue, no matter how many clamps you use....

(I am tossing a caveat in here.... if you try hard enough, its possible to starve a joint, but its highly improbably based on the number of clamps most people use)


2) Clamping pressure at 200 psi for hardwoods is not ONLY good to get max. holding force when the glue dries, but also provide an invisible glue line. In my case, I chase the invisible glue line more than I do the max. holding force of the glues, as most projects I do are never subjected to the levels of force whereas the joint will fail.... Titebond engineers suggest 250 psi of force for hardwoods to close the glue line just a bit below .002". (invisible)


3) Clamping force is consumed quickly, as the force must be divided by sq inches of the joint.... so to meet Titebonds requirements of 250 psi, (for either invisible glue line and / or max. holding), a 1" thick board glue up, would require one 750 lb force clamp every 3" of glue line. 750 lb force clamps are about avg. for most parallel clamps. Hence why I like to see how much force many of these clamps truly exert.... and how long they hold the pressure. I have a handful of the Gross Stabils that are recently being dumped on the market since Bessey bought GS, and they are the worst of all, avg maybe 450 lbs. Even at half price, they aren't worth it.


Anyway, glue pressure always brings out the stone throwers on these forums.... so use the information to your liking. There is many times, I use blue tape as my clamps, and I have never had a problem, but this is for small moldings or edging..... so like everything else, a bit of common sense has to be applied to each application.

[Alan Schaffter]

Clamping pressure is a subjective term until you define it and when you bring the human element into the equation it makes numbers meaningless.

1. Hand torque and other design features aside and assuming near unlimited strength - since the face of the new Revo is larger (more sq. in.), someone theoretically could apply more total pounds. The object, through the face of the jaw, pushes back with more force than a smaller jaw. Now, since hand torque is limited this argument is totally meaningless.

2. If the claim is based on the amount of torque a person can apply to the handle- Revo has a new handle that ostensibly allows a person to grip it better, without slipping, and to apply more torque- so the clamping pressure is greater than the same individual could apply with the old K-bodies. With a toggle handle parallel jaw clamp you could apply even more torque.

3. The only true way of increasing the clamping force for the same individual using a Revo vs an old K-body is to increase the mechanical advantage, either by using a pivoting (lever) handle like the clamps from (?) or to use a finer pitch on the lead screw.

Bottom line, you can't get something for nothing.

Frankly, if you need to apply more pressure than a K-body can deliver, you made something wrong. The benefit of K-bodies or any of the parallel jaw clamps is (1) the jaws are parallel and (2) the clamping face is the adjustable face unlike a pipe clamp- I always hated adjusting the fixed face end of long pipe clamps.

[Will Blick]

I feared this..... I hope the flames remain low...


> Clamping pressure is a subjective term until you define it

I did define it, by the use of a gauge. Clamps produce force, this easy to measure.



> since the face of the new Revo is larger (more sq. in.), someone theoretically could apply more total pounds.


Clamping force is irrelevant of the clamping surface area. It's the sq inches of the glue line that is divided by the total force.



> If the claim is based on the amount of torque a person can apply to the handle- Revo has a new handle that ostensibly allows a person to grip it better, without slipping, and to apply more torque- so the clamping pressure is greater than the same individual could apply with the old K-bodies.


Agreed....and this is what I tested. My point was, the new handle was an insignificant improvement as for gaining more clamping force. It offered no better grip than the wood handles on the K body. Hence my disappointment. It felt a little better, but offered no more in terms of force. As I mentioned, the Stanley Bailey Parallel clamp got the handle perfect...hence the level of force is so much greater...



> With a toggle handle parallel jaw clamp you could apply even more torque.

I thought for sure Bessey would have done this, if for no other reason, it's easier on your hands and fingers... just like a pipe clamp. I bought a few Bessey Chinese knocks-offs from Woodline, whose handle bent 90 deg., but the damn clamp was so poorly made in other areas, I returned them.



> The only true way of increasing the clamping force for the same individual using a Revo vs an old K-body is to increase the mechanical advantage, either by using a pivoting (lever) handle like the clamps from (?) or to use a finer pitch on the lead screw.


Or a better designed handle, the Stanley Clamps demonstrated this with flying colors, they have the same mechanics as all the others, but will attain 30 - 40% more force.



> Frankly, if you need to apply more pressure than a K-body can deliver, you made something wrong.


You need half the number of clamps for a given glue up, if you use clamps that provide 2x the pressure..... that IMO is a significant issue when choosing what clamps to buy.




> I always hated adjusting the fixed face end of long pipe clamps.


Good point.... OTOH, the it's relatively easy to move the rear standard...and if you use black iron pipe, it reduces slippage.... most pipe clamps can easily apply 1200 lbs of force due to their 90 deg. handle. Considering their low price and the fact you need to use less of them, they are quite the bargain...

[Alan Schaffter]

You might want to go back and fix your font, you are shouting.

The "you" was generic, not "you" specifically. Just go back and read the clamp reviews this year in the WW mags- check out their methods for applying and measuring clamping pressure. One mag said they used members of the staff- not scientific, but actually somewhat relevant, since it gave a range of what was possible by each member using each clamp. How about this rating "Jane Board, a 5'3" female of average build and musculature can apply more force with a Schmotz clamp than with a Squeezit clamp, on Tuesdays, with 5 min. rest between clamping, testing the Schmotz first, and no tail wind" That is about all they can truly say, but does it sound good in a magazine ad? No numbers!?!?! Gotta have numbers!!!!! Unfortunately there is too much human variable for any better.

A gauge will measure force applied to a point, so is not relevant to clamping woodworking, and frankly test the person, not the clamp. One person's grip might be better on a triangular handle than a fluted handle of visa versa.

I was talking theoretical force applied by the clamp face, trying to second guess Bessey's logic or method, not referring to the force applied across a glue line.

Ah, Woodline, thanks, I couldn't remember that vendor. Maybe they patented the toggle handle? Maybe Bessey didn't think they needed the extra leverage?

Now the final point, again, I maintain, if you need more force than a Bessey can apply you have done something wrong or your board warped on you. If you have a long glue line you need even force applied along it, so you need either more clamps to spread the force out over the span regardless of the type of clamp, or you need a totally rigid (steel) backer or use something like a Bow Clamp (http://www.bowclamp.com/) which claims by its computer designed bowed geometry to accurately spread the pressure out along the glue line and therefore requires fewer clamps. Even edge gluing/clamping wide hardwood boards you need to use multiple clamps or you chance crushing the outer edge wood fibers.

And the real bottom line- they are all WAY OVERPRICED!!!!!!!!!!!!!!!! Glad I got my Besseys during the frenzy of 6 -7 years ago when you could pick up a K31 or larger for around $12-15$.

[Will Blick]

Sorry about the fonts, I can't seem to edit that? Anyway, shouting is CAPS, not slightly larger fonts...


> How about this rating "Jane Board, a 5'3" female of average build and musculature can apply more force with a Schmotz clamp than with a Squeezit clamp, on Tuesdays, with 5 min. rest between clamping, testing the Schmotz first, and no tail wind"


Of course everyone will apply different force....but that is not the real issue. The issue is.... how each clamp reacts differently in its ability to apply force for the same person. So the results between clamps will be relatively the same ratio differences.... i.e. the Stanley applies about 35% more force than the Besseys, regardless if the persons strength...its a relative difference. Also, there is no reason to turn this into an exact science, if you are a man of avg. strength, these numbers are close enough, no one is trying to get within 10% of accurate results, instead, we are trying to avoid 800% mistakes in lack of clamping pressure.


> Now the final point, again, I maintain, if you need more force than a Bessey can apply you have done something wrong or your board warped on you.


Its the total number of clamps you need, which is a factor of how much force each clamp can provide. If you use Bar Clamps vs. GS parallel clamps, you can use 1/3 the number of bar clamps....... it doesn't mean you did anything wrong, you simply need x bar clamps or 3x GS clamps. Less clamps = faster working before the glue dries....not sure what you find combative about this issue?

[Alan Schaffter]

I guess we will have to agree to disagree. :)

[Will Blick]

Revo at 300 lbs of force after 20 hours.... terrible....

Like a tire with a slow leak....

[Alan Schaffter]

Revo at 300 lbs of force after 20 hours.... terrible....

Like a tire with a slow leak....

Doesn't make sense! Is the handle turning?!??!?!?! If it is then the clamp is bad. If not the gauge tip is compressing the soft jaws, or if wood is involved the fibers are being compressed- technique issue.

[Will Blick]

Alan, the clamp is new...... I will give it a break in period. They all loose tension.... just not this much. Are you under the impression that every new product works perfectly? There is no wood involved, only the clamp and the gauge.... yes, there might be a small amount of compression, but not this much. I will try it a few more times...

The Rockler pipe clamps with the nickel plated bar they sell slips so bad, its barely useful, pressure goes from 1200 lbs to 500 lbs in 30 minutes.... black pipe reduces this 80%.

[Alan Schaffter]

Alan, the clamp is new...... I will give it a break in period. They all loose tension.... just not this much. Are you under the impression that every new product works perfectly? There is no wood involved, only the clamp and the gauge.... yes, there might be a small amount of compression, but not this much. I will try it a few more times...

The Rockler pipe clamps with the nickel plated bar they sell slips so bad, its barely useful, pressure goes from 1200 lbs to 500 lbs in 30 minutes.... black pipe reduces this 80%.

?????
Hmmm, I have NEVER had a Bessey K-Body slip. Really, NEVER. You must have a bad one/batch. My only limitation on clamping pressure using a Bessey K-Body has been the strength of my grip and wrist trying to tighten them.

[Will Blick]

> I have NEVER had a Bessey K-Body slip. Really, NEVER.


How would you know if they slipped? Unless there is gauge on them the entire time, there is no way of telling. When you remove them, you would not know the difference. I have about 9 different brands of clamps, and everyone slips.... a few are terrible, and some slip a little, maybe 15% loss of force over 6 hours....which is very acceptable.

[Alan Schaffter]

You can check for slippage- clamp something, mark the bar with a sharp pencil or a piece of tape at the bottom or the top of the movable jaw, come back later and see if it moved from the jaw moved from the mark. It can also be done with nail polish- paint a bridge between the bar and the movable jaw. Come back later to see if the nail polish has cracked or wrinkled which means movement.

I have had Quick Grip style clamps and various brands of pipe clamps slip, but never had that problem with Bessey 'F' or K-body clamps.

[Will Blick]

It's not that easy Alan..... the bar flexes more over time, surrendering force, specially the Quick Grip style..... the pads compress, the jaws give a bit, the internals of the handle can creep, etc. I used to think the same things you did, till I bought a pressure gauge. I too was easily fooled....

The critical force comes with that last bit of handle turns, I would estimate with the K bodies, the last 40% of the force comes in the final 1/8th of a turn of the handle....

[Alan Schaffter]

It still has to be the testing method.

I don't know what pressure measuring device you are using or how, but if pressure starts to be applied to some very rigid non-yielding object (gauge between the jaws), and the jaws are the slightest bit soft (vinyl or rubber faced by design) then the minutest amount of movement or more likely give in the soft jaw face will equate to a big and likely massive reduction in pressure, and the amount is totally a function of the measuring device. Remember, when you clamp a joint, the wood on either side yields, and is compressed, so even if the jaw faces compress or the clamp relaxes slightly there is little to no reduction in pressure exerted on the joint. I think that is what is happening. If the clamp jaws do not move then the clamp is working as designed and likewise the pressure exerted is constant.

When K-body bars bend, a LOT OF FORCE is being applied, likely more than needed, in view of the size of the nickel-steel bars on a K-body.

[Will Blick]

> It still has to be the testing method.


hmmm, with no real world data, you come to this conclusion? shoot the messenger?




> I don't know what pressure measuring device you are using


It's a pressure gauge, designed to test the force exerted by clamps.




> or how, but if pressure starts to be applied to some very rigid non-yielding object (gauge between the jaws), and the jaws are the slightest bit soft (vinyl or rubber faced by design) then the minutest amount of movement or more likely give in the soft jaw face will equate to a big and likely massive reduction in pressure, and the amount is totally a function of the measuring device.


The gauge has a 1 sq inch surface area.... When I first got the gauge, I sandwich the gauge between two pieces of metal, to see if the smaller area would effect the results, the results were identical... slippage was the same.... force was the same.




> Remember, when you clamp a joint, the wood on either side yields, and is compressed, so even if the jaw faces compress or the clamp relaxes slightly there is little to no reduction in pressure exerted on the joint.


I am working from real world test results. You are working from "wishful thinking". Before I got a gauge, I thought many of same thoughts you did. But I never had the benefit of reading results from someone who tested this with real gauges. If I did, it would have influenced my thinking..... obviously, we react differently to real world data.



> I think that is what is happening. If the clamp jaws do not move then the clamp is working as designed and likewise the pressure exerted is constant.


If you wait a few days, the pressure often falls to 200 lbs..... and this is considered NO loss of pressure ? OK....




> When K-body bars bend, a LOT OF FORCE is being applied, likely more than needed, in view of the size of the nickel-steel bars on a K-body.


LOT OF FORCE = the amount of force Bessey advertises the clamps to be designed for, i.e 1000 lbs of force. But since this is unattainable, I am usually working with 800 lbs starting force. The greater the length, the greater the flex. It only takes very small amount of flex to loose force.


I am curious..... just how perfect do you expect a $25 clamp to be? I am not knocking the clamps, I am quite impressed they can make such a nice product for the price they sell it for. But at the same time, I am a realist, and understand a $25 clamp is NOT perfect under all working conditions....you obviously feel different. In most cases, where we use fast dry glue, slippage is usually not an issue, but slower drying glue, like plastic resin glue, it can be a BIG issue. In such cases, I continually re-tighten my clamps.

[Tony Zaffuto]

Would you mind a guy from the "hand tool" section asking a dumb question? What is it you guys do, that requires this much pressure?

T.Z.

[Douglas Brummett]

I took a look ate the revo the other day in lowe's. Honestly I can't figure where the 25% would come from. The handle is about the same diameter and the composite they use feel slippery to me (maybe that is just mold release and grip will improve with use). I was actually a bit dissapointed. I have a good collection of k-bodies already and recently got 6 jet clamps. The jets are big and burly, pretty much dwarf the k-bodies on the shelf.

On paper the new revo looks like it is beefed up to compete with the jet clamps. In reality they are not in the same league. If Will's results are indicative of the product they may have dummed down the k-body to dissfunctional by "upgrading" the design :rolleyes:

[Will Blick]

>I can't figure where the 25% would come from. The handle is about the same diameter and the composite they use feel slippery to me


Doug, I agree, hence my previous comments, where were met with EXTREME resistance. I only bought one Revo to test, so I will give it some break in time.... I agree with your assessment of the Revos... i think they went after Jet, vs. making major improvements in the clamp. The handle would be fine if they added a joint allowing it to be 90 deg. to the threads to ease the pressure on the hands...


> What is it you guys do, that requires this much pressure?

We clamp wood together.... 800 lbs of force divided by a 1" thick glue up, over 10" is only 80 lbs psi, much less than is suggested by glue manufacturers. Force gets consumed quickly by a long glue joint.

[Alan Schaffter]

You didn't say if you checked for jaw movement? Run your test again, just as you described, but instead of making a mark like I suggested previously (likely not accurate enough to measure), put a dial indicator between a metal part of the other jaw or the bar and a metal metal part of the movable jaw- this may not be easy to find two hard points. See if the jaw moves over time. If it does, then the pawls inside the head are not properly gripping and holding the bar or the metal is too soft, too much backlash in the lead screw, etc. and the clamp is defective and/or poorly designed.

Again, I maintain, unless the jaws move (head slips on the bar or screw handle turns), the only way there will be any reduction in clamping force is if something yields under pressure- like the soft jaw faces.

Another way to test this (and evaluate the effect on your pressure gauge) is to use two pieces of similar (density and thickness) jaw face material, your pressure gauge, and a heavy duty machinist vise. Put the pressure gauge and face material between the vise jaws, and crank it up to the pressure you are using to test the clamps. See what happens. If the pressure drops off, then you know the reason. If it doesn't see the first test.

Don't get me wrong, I am not challenging your results, just trying to narrow down the reasons and possible causes.

[Brent Smith]

> What is it you guys do, that requires this much pressure?

We clamp wood together.... 800 lbs of force divided by a 1" thick glue up, over 10" is only 80 lbs psi, much less than is suggested by glue manufacturers. Force gets consumed quickly by a long glue joint.

Hi Will,

I'm not disagreeing with your tests, if you say that's what you're getting that's good enough for me. I do, however, have the same kind of head scratching question that Tony had, why the need for so much pressure. I've glued up short and long glue ups with my K-Bodies and never had to exert maximum force on them, also never had a glue joint fail that wasn't caused by lousy prep work, or using the wrong glue. If the mating pieces are properly milled there is no need for that kind of force. I bring the joint together and give the clamp a little extra turn and I'm done.

I have to admit that I find your testing interesting in that it shows that the advertised pressure for the new clamps may be a bit on the stretched side, but then again, that quite frequently is the nature of advertising.

[Tony Zaffuto]

Thanks Brent, you said better what I wanted to say!

I have some Bessey K-bodies, but most frequently use my Jorgensen light duty F-style clamps. Correct joinery does not require extraordinary pressure on the wood to pull the joint together. Clamps are meant more to hold a piece stationary while the glue sets up.

The main criteria I apply to clamps is convenience of use, meaning which are the easiest to set-up and adjust during a glue up.

Tony Z.

[Will Blick]

Hi Brent / Tony.... post #6 above, addresses all your questions...

The only additional comments I will offer, to zero in on your question is.... manufacturers have stated the amount of psi required at the glue line to achieve both max. holding force the glue is capable of and an invisible glue line. If neither of these two issues are important, then obviously, there is no need to apply this level of force. Hence why i stated, there is many times when I use blue tape as my clamps, and it suffices just fine for a given light task.

However, even when boards are freshly milled, and glued within an hour of being milled, makers still never suggest less than 75 psi. The 250 psi is to overcome the slight movement after an hour of milling.... of course, if you wait days, even 250 pis might not be sufficient to make even contact along a long joint line.


Again, many variables at play here, and clamping force can range from rubber bands to a load of parallel clamps... its all according to what you are gluing and the intended end-use. Whenever these posts are made, everyone seems to jump at the high pressure clamping applications and wants to make a point about how much less pressure they use. They somehow ignore the comments in the same post, about blue tape and rubber bands often being more than sufficient for many tasks......


Alan, the pads don't compress enough to attain this level of slippage. When clamping wood, the wood can be a variable, but my tests are done without wood. So yes, it only makes sense that the jaw slips on the bar... as well as some flexing of the jaws as well as the bar... After i learned this, I just re tighten often when using slow dry glue...

[Brent Smith]

Titebond engineers suggest 250 psi of force for hardwoods to close the glue line just a bit below .002". (invisible)


Given Bessey's stated clamping pressure for the new Revos, and the conclusions you got from your tests, I have to wonder about the above statement from Bessey. Could it be that this amount of pressure is also overstated? I doubt very much that I use that much pressure and I get very tight, if not invisible, glue lines in my panels. Anyway, I want to thank you for posting the results from your testing on the new clamps.

[Peter Quadarella]

Will, have you tested 3/4" Pony clamps with black pipe? I'm curious how they stack up since they are my primary clamp (along with HD F style Jorgensons and Jet Parallels, and the old wooden ones).

I don't think it makes sense to ask why we need to clamp hard, in a thread comparing clamping pressures. Even if we all used spring clamps for everything, I would still be interested in the relative clamping pressures of different clamp styles, especially since some advertisers are using these claims as a selling point.

[Will Blick]

> I have to wonder about the above statement from Bessey.


As mentioned, marketing guys stretch the truth about everything. I guess if Arnold used the clamps, he could squeeze the extra 25% force from them....but not us mortal men :-)



> Could it be that this amount of pressure is also overstated?


There is no reason for glue makers, and other USDA research labs to overstate the amount of glue pressure required. Instead, they state the accurate amount of psi their testing reveals. All titebond stats clearly state, these results are based on 250 psi clamping pressure.


Does that mean every joint has to achieve the max. holding pressure the glue is capable of? Heck no.... As you mention, you use much less, and your glue joints are adequate.


As for invisible glue lines, this is often a function of how long the glue joint is, and how straight the joined edges are.....which is where elapsed time since milling comes into play.... So there is many variables at play here. If the joint line is 4", even lousy jointed edges will join well, but not true when you have a 60" glue line. hence why i keep saying, the right clamping strategy is a mix of good ol fashion common sense combined with the available knowledge.

[Will Blick]

> have you tested 3/4" Pony clamps with black pipe?


No, I don't have any Pony's, but my guess is, with black pipe, they perform very well.... the softer the pipe, the less the slippage...and if they have the T handle, you can really get max. force, 1200 lbs.



> I don't think it makes sense to ask why we need to clamp hard, in a thread comparing clamping pressures.


Thank you for this :-) It seems whenever you offer info on clamps, the immediate question is, why clamp so hard?? I tried to difuse it early in the thread...but.... but here on the creek, everyone is civil, so no biggie.....



> Even if we all used spring clamps for everything, I would still be interested in the relative clamping pressures of different clamp styles, especially since some advertisers are using these claims as a selling point.


Exactly..... that's the point here.... I just want to understand what the heck I am buying? I consider a clamp that can easily reach 1200 lbs of force, to be more valuable than one that can only achieve 600 lbs. Regardless how I use it...


IF the Stanley Bailey parallel clamps could be joined, like the Besseys, I would use them exclusively. Its amazing how they entered the Parallel clamp game so late, and yet, produced an amazing product at a fair price. But I can't deny the value of being able to join the Bessey K's for those few occasions where I need long clamps. The Jets can be joined also, even though not advertised... as such... although i have not done it..... there was a thread here awhile back showing such....


Also, if you build up the handle on any of these clamps, you can add about 25% max. force you can achieve to the clamp. That was a very interesting finding....and it proves why the Stanleys are so damn good, not only is there handle triangular to prevent slipping, the handle is massively thick compared to the rest of these makers. hence why the Revos new handle dissapointed me. They missed both of these Stanley handle enhancements.


I built my K's up with some grip wraps that LV sells, as well as some close-out tennis grips, which work great for $1 each. I build the handle diameter up about 30 - 40%... I marvel how the damn gauge moves up 25% in force... makes me feel stronger :) ....oh yeah, easier on your skin too....


Interestintly enough, as robust as the Jets are, they too fall way short of their advertised pressure claim....some of my jets I can only push to 650 lbs, others to 800 lbs. I think their threads are not consistent, poor QC. The K's are more consistent.

[Brent Smith]

As for invisible glue lines, this is often a function of how long the glue joint is, and how straight the joined edges are.....which is where elapsed time since milling comes into play.... So there is many variables at play here. If the joint line is 4", even lousy jointed edges will join well, but not true when you have a 60" glue line. hence why i keep saying, the right clamping strategy is a mix of good ol fashion common sense combined with the available knowledge.

No argument from this corner of the peanut gallery :).

[John Gornall]

Recently I had a large number of items to glue up - glued and clamped every hour for 3 days. Using K bodies my hands were in rough shape after. Funny how the work gets so important you don't notice the physical damage as early as you should - just gotta get the work done. Then yesterday I was gluing up a garden gate with a series of 14 large mortise and tenon joints. I had done a dry fit and all was smooth but in the final assembly with glue as happens now and then it just wasn't pulling together. My hands were hurting on the K bodies. I removed the K bodies and laid on the good old pipe clamps pulling the gate together easily. Now I'm looking at the K bodies and thinking about removing the wood handles and welding or pinning on a nut so I can use a ratchet wrench. I could also make a screwdriver handle with a socket for basic tightening. Those wood handles on K bodies are not good and hard on the hands.

[Will Blick]

> Those wood handles on K bodies are not good and hard on the hands.


Nothing like repetition to expose the weak link in the chain, huh? If you want to replace the handle, use the pipe clamp method, way easier on the hands and you get almost 2x the force from the clamp.... I can't fathom why the parallel clamp makers did not copy the pipe clamp handle design.... the force comes from leverage, vs. grip strength and ripping the skin off the inside of your hands....which when you do it a lot, can be irritating :mad:


Even though the Stanley Baily has the primo grip, it is NO match for the pipe clamp leverage handle..... let us know what you do! I have been too lazy to consider replacing the grips...

[Ron Dunn]

Do we care?

All I want to do with a clamp is hold stuff together while glue dries. I'm not trying to turn carbon into diamonds!

[Will Blick]

As mentioned, clamp pressure brings out the hecklers.... they can't resist.

Question: If you don't care, why are you reading the thread? Thats the real qustion!!! :)

[Ron Dunn]

It was a serious question. I'm curious about the woodworking circumstances in which this could be considered important.

I'm sure I've heard that too much pressure is as bad as not enough.

I'm also thinking of the woodworkers in times past, when joining a panel was by rubbed joints, with no clamps at all.

[Will Blick]

> I'm not trying to turn carbon into diamonds!

that certainly did not seem sincere to me?


Ron, if your questions was sincere, the answers are all above in this thread.... they have been repeated at least 5x now. Often, rubber bands will suffice for clamping pressure. Rubber bands will not turn carbon into diamonds.


However, that does not dismiss the need for clamps in some critical glue ups. At such time, it pays to understand how much force the clamps you use can apply.... assuming you want to follow manufacturers recommendation for max. hold and / or invisible glue lines.

[Ron Dunn]

The QUESTIONS have been asked, but the ANSWERS have not been forthcoming.

Is there any circumstance where over 800 pounds of pressure is necessary for a woodworking joint?

Sometimes obsessing over a detail obscures the fact that the detail is irrelevant.

[Will Blick]

> The QUESTIONS have been asked, but the ANSWERS have not been forthcoming.


AS mentioned Ron, it's all written in this thread.... getting tired of writing the same thing over and over.... ONE LAST TIME....


> Is there any circumstance where over a thousand pounds of pressure is necessary for a woodworking joint?


I think you are missing the connection between the pressure (force) vs. psi at the glue joint. Simple example....if you follow the guidelines for max. glue holding force and /or invisible glue line, you need about 200 psi at the glue line. If the boards are 1" thick, and 48" long, this is 48 sq in. of glue line. 48 * 200 = 9600 lbs of total force required. If your clamps "CAN" hit 1000 lbs of force, 9600 / 1000 = 10 clamps required. So in this example, you can safely use up to 9600 lbs of force. Is this mandatory? Of course not....it's suggested for max. holding force of the joint and / or an invisible glue line....



> Sometimes obsessing over a detail obscures the fact that the detail is irrelevant.


Glue makers and wood researchers spend millions of dollars obsessing over these details....they provide their findings to us for free. Whether a ww wants to implement their suggestions is a personal choice. Commercial shops that have pneumatic clamping systems which can provide a wide range of pressure.... they have to set their clamp pressures on the machine, this is an example how they determine such... OK? Irrelevant? Maybe to you and me, however, others do take heed to what manufacturers suggest.


I predict this will not be the end of ....

Why so much pressure questions.... arggggg....

[Tony Zaffuto]

Will, please don't take this as "heckling" as it is certainly not meant to be. I understand the need sometimes to have sufficient pressure to wrestle a couple of pieces together.

My issue, however, stems from the later reaction of the wood and glued-up joint, to that action. I am not denying one bit that sometimes you need all the force you can muster to close up a joint--I have had those occurrences, for example when a glue-up does not go according to plan.

My thoughts are that more attention needs to be made to prepping the assembly to prevent later reactions to the piece six months or a year after finish has been applied and it goes through the first temperature/humidity change in its final resting spot.

Now with this post, I will return to my knuckle-dragging brethren in the hand-tool sections. You guys need to visit some of those sites to see what real heckling is (certainly not done by me!).

Tony Z.

[Will Blick]

Tony, this post is certainly not heckling.... and it raises some often overlooked issues....


> My issue, however, stems from the later reaction of the wood and glued-up joint, to that action.


Interestingly enough, when speaking to a titebond engineer / chemist at a ww trade-show, he mentioned.... the most overlooked reason to attain max. glue adhesion (through sufficient clamp pressure) is to prevent wood movement from opening the glue line. He suggested, more often than not, the biggest load on a glue joint is wood movement, NOT mechanical loads placed on the joint. Which is what most of us think of...

A few years ago, this changed my mind-set from, "just glue it" ...to.... "glue it right" Of course, I get sloppy at times...but if the work piece is important, I give the glue line more attention.


> My thoughts are that more attention needs to be made to prepping the assembly to prevent later reactions to the piece six months or a year after finish has been applied and it goes through the first temperature/humidity change in its final resting spot.


Can you share some of these tips? I think NOT enough information is provided in this area.

[Rod Sheridan]

I normally use the K body clamps for glueing, however I also have many Jorgenson pipe clamps.

With hardwoods, I tend to use fewer clamps per joint, since the wood is stronger and resists crushing better. I can tighten the clamps up very tight, and achieve good clamping pressure by using fewer clamps, applying more force per clamp. This is significant, since I can use less clamps per piece, I just need to be able to apply more force per clamp.

With pine, I use more K bodies along the joint, and don't tighten them up as much. I get the same pressure by using more clamps with less force.

Since I am probably below median strength for an adult male, I wish that Bessey made a better handle for their clamps, so I could take full advantage of their clamping strength. Otherwise, I think that they are the best clamps I own.

P.S. When my FIL worked in industry, the panel glue ups were performed in a rotating panel clamp jig. The number of clamps, and the torque applied to the clamp screw was calculated, and the clamps were tightened with a pneumatic torque wrench. This was part of the work sheet information for the panel assembly. Even 30 years ago someone was thinking about clamping pressure. I was pretty impressed seeing that.

Regards, Rod.

[Tony Zaffuto]

Will,

You asking the wrong person (a hobbyist) for tips! There are things I do, but these I have learned from listening and watching others.

A few things I do, is make sure wood I am using is fully acclimated to my basement shop before using. For example, I'm working on a side table and the cherry I'm using has been in my shop for over six months, after being supplied to me kiln dried. I have the 1/2" poplar for drawer sides and bottoms also acclimating. Further, I usually only use quartersawn or rift sawn wood for table tops. Beyond that, I just try to apply good joinery--not sloppy joints, but also not joints that I need a ton of pressure to close! I also usually use a sprung joint for table tops.

In the past, I have observed movement in a few pieces I have made and that is the reason I'm sensitive to this issue. You made a very good point about glue strength too: often times the glue joint is far stronger than the wood itself. With wood movement, then, a crack can occur in a location away from the glued-up joint splitting the wood!

In closing, I may have missed the intent of this thread as purely a discussion of relative clamping pressures and to other posters, I apologize for that. Now as a "knuckle-dragger" I may be inclined to heckle a bit using some other verbage, such as asking why you power guys just don't resort to using hide glue and rubbed joints? You may not even need a clamp then!

You all have a good one said while ducking and running, and if you're going to through clamps my way, make sure they are (two) 72" alumimun made by Universal Clamp Co., as I got to do a glue up on the side table I'm making in a week or so.

T.Z.

[Scott Pearson]

When I saw the new Revo clamps I wondered why they did not do more to change the handles. Making the diameter of them wider or even changing the shape to a rounded triangle would have added more torque allowing for clamping pressure.

I stocked up on the big Bessy sales, I guess I should look for a few more.

Scott

[Will Blick]

> You made a very good point about glue strength too: often times the glue joint is far stronger than the wood itself. With wood movement, then, a crack can occur in a location away from the glued-up joint splitting the wood!


This is very true.... however, the hope is, the wood has enough flex to prevent it from cracking elsewhere. But if the glue joint is not as strong as the wood, then the crack will occur in the glue joint...sometimes making for an easier repair.... so pros and cons I guess....

I wonder sometimes how all glue to wood joint is not stronger than the wood itself. Quite often, i spill some glue on a scrap piece, and it comes into contact with another scrap piece.... when I go to break them apart, 80% of the time, the wood parts before the glue....hence why at times, I am not scared of rubber bands and blue tape :-) But this is not the same as a long glue line... where parallel issues come into play.


A lot of the basics you covered well..... how often its easy to overlook the simple things...which cause even bigger problems... I certainly see the value of veneered MDF, as at least you don't have to worry about wood movement...

[Verne Mattson]

The issue of clamp slippage is a valid one...I never really thought about clamps slipping in a normal clamping situation. I would think it would matter most when you're veneering or laminating.

Would a slipping clamp cause a weaker cure in a normal joint?

Whether or not a slipping clamp affects a joint, I think I'd stay away from buying any clamps that slip significantly, so it's helpful to know.

[Will Blick]

> Would a slipping clamp cause a weaker cure in a normal joint?


Great question.... I think if enough slippage occurs before the glue has dried, the answer is yes. If the slippage occurs after the glue has dried, then NO.


So if you use fast set glue, you are probably safe.... slow set glues, just remember to re-tighten every 2 or 4 hours. When you initially tighten your clamps, tighten them as hard as you can, so you have a benchmark. Then when you re-tighten, you can see how much handle turns, this will advise you how much slippage your clamps have.


Here is a good rule of thumb.... on parallel clamps with standard acme threads, such as the K's, the last 1/5 of a turn = 400 lbs of force. (half the total force) I just went and confirmed this. So if you re-tighten and can turn 1/5 turn, you lost 400 lbs of force. Test some clamps on some scrap, let it sit for x time, and see what happens. If you have NO slippage, you will not be able to re-tighten. Use a hardwood or metal.


This is a reason why clamps with tighter threads would be more ideal, as you don't have all that force applied in such a limited rotation range, hence why I have blisters :-)

[Dana Vogel]

I found the rubberized handles to be slippery yielding a less than ideal result I did not measure the results but feel confident it would have been less than the originals. I do like the less aggravating locking setup of the Revo's but not worth the xtra mullah.

[Chris Padilla]

Will,

Interesting thread. Would you care to provide some pics of how you measure these things? They are often worth a 1000 words. :)

I see no mention of cauls in this thread either. They can help one to use less clamps and spread the force from them more evenly.

[Will Blick]

Chris, I use a standard mechanical pressure gauge...

As for cauls.... at best, a caul will only distribute the total force more evenly.... it does not change the total force required, which is what this thread is about...


here is Revo after 4 hrs, 800 - 425 lbs....
Jet performs about 20% better on slippage, but lots of variance between samples...

http://www.pbase.com/image/103632137


Here is Stanley Bailey after 4 hrs, 1100 - 1000 lbs

http://www.pbase.com/image/103632192

[Alan Schaffter]

Will,

Interesting thread. Would you care to provide some pics of how you measure these things? They are often worth a 1000 words. :)

I see no mention of cauls in this thread either. They can help one to use less clamps and spread the force from them more evenly.

I mentioned Bow Clamps :)

I too would like to see the test setup or see specs on the force gauge. Here is my reasoning. If you have a force gauge between two non-compressible jaws, how much movement is there in the gauge's internal mechanism- a load cell (if digital, usually a strain gauge, but could also be a hydrostatic or other load cell) when the force is increased from 0 to 1000#?? It depends on the design of the gauge but I could not find typical data. If the gauge's internal mechanism moves only a few thousandths, few ten thousandths, or likely even much less (based the designs I looked at) when measuring from 0 to 1000# then it is completely possible that if a force gauge is inserted between compressible jaw faces like on Besseys and other clamps, and even if the face material only compresses ever so slightly, the pressure reading could be greatly reduced and in error.

[Will Blick]

> It depends on the design of the gauge, right? If the gauge's internal mechanism moves only a few thousandths, or ten thousandths, or even less when measuring from 0 to 1000# then it is completely possible that if a compressible jaw face or two is inserted into the setup and if it only compresses ever so slightly, the pressure reading could be reduced or greatly reduced.


Alan, pressure is pressure. It doesn't matter what the force vs. movement ratio of the gauge is. Who cares where the loss of pressure comes from...the clamp designers need to consider all this when designing a clamp, not us, we are end users.


If the jaw material compresses, then when I re-tighten them, why do they loose pressure again? Get my point here? yes, it may be a small contributing factor, but thats the clamp design, and therefore that's what you get when you buy that particular brand.


I realize you have been stuck on this position, but it really is irrelevant. The general purpose of a ww clamp is 1) create force, and 2) hold the force. These test measure both of these two criteria. I am not concerned with "why" they don't create enough force, or why the slip. Some clamps fail none of these, some fail one, some fail both... that is the purpose of testing them. Make sense?

[Alan Schaffter]

It depends on the design of the gauge, right? If the gauge's internal mechanism moves only a few thousandths, or ten thousandths, or even less when measuring from 0 to 1000# then it is completely possible that if a compressible jaw face or two is inserted into the setup and if it only compresses ever so slightly, the pressure reading could be reduced or greatly reduced and in error.



> Alan, pressure is pressure. It doesn't matter what the force vs. movement ratio of the gauge is. Who cares where the loss of pressure comes from. . . .

I hate to differ, but you are absolutely, completely, wrong. It matters alot!!! It is only a non-factor when measuring between non-compressible surfaces. People care if the loss of pressure is only in your testing!


If the jaw material compresses, then when I re-tighten them, why do they loose pressure again?

Because the vinyl/hard rubber jaws continue to compress!!!!!!!! Drill a hole in the jaw face or remove the jaw face and test pressure between the metal faces and you won't lose force. It is that simple, and the answer, as always, has been flawed testing!!!!!!


I realize you have been stuck on this position, but it really is irrelevant. The general purpose of a ww clamp is 1) create force, and 2) hold the force. These test measure both of these two criteria. I am not concerned with "why" they don't create enough force, or why the slip. Some clamps fail none of these, some fail one, some fail both... that is the purpose of testing them. Make sense?


Not irrelevant. Your test measures neither criteria. These clamps will apply as much force as a person's wrist and the thread pitch of the lead screw will allow- that is their only weakness- the mechanical advantage or lack thereof of the handle design! Their clamping pressure does not decrease over time, it is only a function of your testing!!!

I suggest you do some research on force gauges, their proper use, and mechanical engineering.

[Will Blick]

Alan, your positions baffle me. Putting aside my 25 years experience as an energy engineer.... lets just approach this from simple laymans perspective.


1) The test results are the same (usually worse) when wood is inserted between the jaws and a clamp is between the wood and the jaws. That is the intended use of the clamp - so why would this not be a true indication of what is happening to the joint when being clamped during a glue up? And, why does a ww care about why the clamp looses pressure? The key here is, knowing if the clamp looses pressure over time, AND, how much force a clamp can generate upon initial tightening.


2) When you clamp an object with these parallel ww clamps, any shortcoming of the clamp, which includes compression of the jaw material, slippage on the rail, the handle reversing itself, the bar flexing, jaws flexing, etc. will surface in this test. Some of the shortcomings surface during the initial tightening, which explains why some makes produce inferior intital force, while other shortcomings surface over time, which is why I test the clamps over x period of time.


3) Your position regarding the jaw material compressing as being the culprit, and therefore there is NO problem.... as you suggest this is only a faulty test, but not a problem in the real world.... this conclusion is beyond absurd. Even though I tried to explain this in my previous post, but you completely ignored my response, as you refuse to let go of your intial assertion. I will try it one last time.

As absurd as it is, lets play out your scneario.... I test like you see in the pix. I tighten to 800 lbs, then as per Alan logic, the jaw material compresses, the clamp looses pressure, right? Now, I re tighten to 800 lbs..... a few hours later back to 400 lbs. again and again and again.....

now, is it your position the jaw material has continued to compress each time, hence why the clamp keeps loosing pressure....if so, why isn't there massive indents in the jaw material where the gauge is making contact? I can run a straight edge flush on the jaw surface before the test, and do it again AFTER the test........ Is it clear, compression of the jaw material - IS NOT THE PROBLEM ALAN!!!!!

Also, don't you think that Bessey and the other premium clamp makers are aware of the jaw material compression issue? Or possibly, just today, you were the first person in the world who brainstormed this? Lets get real, they invest big R&D into these clamp designs. The reality is, these are very low cost clamps.... a good metal working clamp cost $500+ each. For the price we pay for these ww clamps, I still consider them a bargain.... do you really expect a $25 clamp to be perfect? Regardless, it still makes sense to test clamps if you want to monitor their relative performance against each other.... and without a gauge, it's impossible...


Next, why do the metal pipe clamps also loose pressure, there is no jaw material to compress, its all metal to metal, right?


Whats your next theory ? :-)

[Jason Beam]

Having read all this ... boy ... it's gettin' heated...

Go ahead and blame the jaw compressing. Fine with me. It came with the clamp, so the clamp lost pressure. The test, by having exposed a potential weakness in the jaw material, is that much more valid is it not?

The test is immediately useless to me if you strip the clamp down to it's metal parts. That isn't how I'm gonna use the thing, so I don't care how valid that test is - I like real world testing not vacuum isolation of factors testing. Yer gonna use the whole dang clamp, right? So how smart is it to test the whole thing AS IS? Seems silly any other way, to me.

I don't need that much force ... well I don't need a car that can go 120mph, either. Sometimes to be really good at middle, you have to be able to achieve well above middle. I wouldn't want to run any clamp at it's absolute maximum designed forces all the time - that's asking for failure.


Look ... the test was "What happens to a clamp's pressure over time?" and that's exactly what was tested. He measured the entire clamp's pressure as it would be used in the real world. About all he could have done differently was stick the gauge in a wood sandwich.

And if he does (please do!), i'll predict the outcome:

The wood will compress some. The theoretical jaw compression will also occur. He'll retighten the clamp back to max pressure. Then... the wood might compress some more, sure. A few iterations of this and there will be no more compression by niether the wood nor the theoretical soft jaws. Then the pressure will come down some more - and to what will you attribute that?

[Will Blick]

> That isn't how I'm gonna use the thing, so I don't care how valid that test is - I like real world testing not vacuum isolation of factors testing. Yer gonna use the whole dang clamp, right? So how smart is it to test the whole thing AS IS? Seems silly any other way, to me.


Sheeehs, some sanity has returned.....thanks Jason, seems so simple, you wonder how anyone can argue it? Well, welcome to the internet forums!


> The theoretical jaw compression will also occur. He'll retighten the clamp back to max pressure. Then... the wood might compress some more, sure. A few iterations of this and there will be no more compression by niether the wood nor the theoretical soft jaws.


As I have stated, i have done this....and yes, the wood is a factor, but using hardwoods, its a very small factor. Of course, if you edge glue several wide thin hardwood boards, you can create a bow of the boards, creating more loss of pressure. You need to sure the glue up in the bow direction. But when face joining hardwoods, the compression of the wood is not really a factor. The loss of pressue comes from the clamps, PERIOD! 800 lbs of pressure is a lot of force for a $25 clamp to hold....Kudos to Stanley for doing such a good job at it vs. the K's.


Jason, your thought process is the same as mine..... most of these ww clamps slip... plain and simple. For a fast glue using Titebond II or III, its not an issue... you need x force for maybe 20 minutes..... however with Poly glue or epoxy, just re-tighten them on a regular basis.... IMO, not such a big deal....but good to know, so you can counter act the slippage. On the standard size parallel clamps, between 1/4 and 1/5th of a revolution on the handle = 400 lbs of force....(of course this has the human strength variable, which I would consider myslef avg.) with that, you can estimate how much pressure your clamps are loosing over time...... it all seems so simple....

[Alan Schaffter]

Alan, your positions baffle me. Putting aside my 25 years experience as an energy engineer.... lets just approach this from simple laymans perspective.


1) The test results are the same (usually worse) when wood is inserted between the jaws and a clamp is between the wood and the jaws. That is the intended use of the clamp - so why would this not be a true indication of what is happening to the joint when being clamped during a glue up? And, why does a ww care about why the clamp looses pressure? The key here is, knowing if the clamp looses pressure over time, AND, how much force a clamp can generate upon initial tightening.

No, lets approach this from 30+ years of mechanical engineering perspective. "Tests" (and real world wood clamping) of any compressible material will always yield a reduction in "measured" force over time, unless that compressible material reaches a point where further compression is impossible, and starts to "push back" with the same amount of force as that applied (Newton's Third Law) since it is a "closed system." Until it reaches a condition of static equilibrium the force will change. But that is not the clamps fault! As you say just retighten. Experience, feel, glue squeeze out, etc. are the only ways (non-industrial) woodworkers have and have always had to judge clamping force, regardless of how the clamp is rated.


2) When you clamp an object with these parallel ww clamps, any shortcoming of the clamp, which includes compression of the jaw material, slippage on the rail, the handle reversing itself, the bar flexing, jaws flexing, etc. will surface in this test. Some of the shortcomings surface during the initial tightening, which explains why some makes produce inferior intital force, while other shortcomings surface over time, which is why I test the clamps over x period of time.

When you test or clamp with any type of clamp you may see any or all of those issues. In order to compare clamps with some type of test, however, the physical conditions must be identical- the means of applying force, measuring force, how much force, to what material, over what area, for how long, at what temperature, etc. etc. As far as clamp manufacturers claims, they can only be verified when using the exact same test as they did. Over the past two years the WW mags have done at least three tests of clamps- no two sets of results are the same!!!!!!!!


3) Your position regarding the jaw material compressing as being the culprit, and therefore there is NO problem.... as you suggest this is only a faulty test, but not a problem in the real world.... this conclusion is beyond absurd. Even though I tried to explain this in my previous post, but you completely ignored my response, as you refuse to let go of your intial assertion. I will try it one last time.

As absurd as it is, lets play out your scenario.... I test like you see in the pix. I tighten to 800 lbs, then as per Alan logic, the jaw material compresses, the clamp looses pressure, right? Now, I re tighten to 800 lbs..... a few hours later back to 400 lbs. again and again and again.....

No pics visible. Again, please go back and dig out and review your undergrad engineering books. I'll try to explain. (You still haven't told us what kind of force gauge you are using.)

If you look at the internal design of most digital force gauges, they rely on deformation of an internal strain gauge, either directly or though mechanical, hydraulic, or pneumatic, linkages. The amount of deformation per # is based on the design of the strain gauge. The deformation of the internal strain gauge results in a change in its resistance which is electrically measured. In the vast majority of gauges a VERY,VERY, VERY SMALL amount of deformation = equals a VERY LARGE amount of force. So when you move the jaws of the clamp against an object that compresses, or if the jaws compress, and do not spring back with the same amount of force and distance as the strain gauge, then you see a reduction in applied force. That can occur almost instantly or over time. Again, not the fault of the clamp. The ONLY exceptions are active clamps (hydraulic, pneumatic,electric) that have a pump or motor and that continue to apply a constant force via jaws or clamping surfaces with the ability to move. Since parallel jaw clamp jaws do not move, tighten or take up slack by themselves, nothing has changed with the clamp or its ability to clamp, but the force being returned by the compressed object is less as is the applied force and the gauge reading.


now, is it your position the jaw material has continued to compress each time, hence why the clamp keeps loosing pressure....if so, why isn't there massive indents in the jaw material where the gauge is making contact? I can run a straight edge flush on the jaw surface before the test, and do it again AFTER the test........ Is it clear, compression of the jaw material - IS NOT THE PROBLEM ALAN!!!!!

Yes, compressible objects continue to compress, depending on the their physical makeup. It usually decreases as time goes on. It is only a problem in your testing!!!!! You would likely need a very precise micrometer to measure the deformation in the jaws, and it may even be difficult in wood, especially with wide jaws. With the vinyl jaws, we may only be talking deformation in the sub-micron range. Remember what I said about the minute deformation of the strain gauge!! In the case of wood glue ups, the deformation of the wood is much greater so even at the beginning of clamping, you typically install the clamp, tighten (it compresses the wood and glue squeezes out ), you tighten some more (it compresses the wood more and more glue squeezes out) until you are satisfied with the amount of force. Typically you clamp a joint with enough force so that the wood and the glue start pushing back with the same force you want to apply to the joint. Jaw deformation is only an issue if you are putting your force gauge directly between the clamp jaws and not an issue clamping wood because the deformation and spring back of the wood overcome it.


Also, don't you think that Bessey and the other premium clamp makers are aware of the jaw material compression issue? Or possibly, just today, you were the first person in the world who brainstormed this? Lets get real, they invest big R&D into these clamp designs. The reality is, these are very low cost clamps.... a good metal working clamp cost $500+ each. For the price we pay for these ww clamps, I still consider them a bargain.... do you really expect a $25 clamp to be perfect? Regardless, it still makes sense to test clamps if you want to monitor their relative performance against each other.... and without a gauge, it's impossible...

Again, deformation of the jaws is not a problem to me, to most woodworkers, nor to clamp manufacturers, it is only an issue to you and your testing. I never said Besseys were perfect, that is all I use, except when I clamp small or irregular stuff and another type of clamp is more appropriate, or when I use pipe clamps for a long reach. If one clamp isn't enough, I use two; if two aren't enough, etc. For long edge glue-ups I use enough clamps so that (1) I have applied enough force for proper glue squeeze-out, and since I don't have fancy cauls (2) the clamping force is evenly distributed so I don't have point stresses. Again, see my comments above about comparative testing and using a force gauge.

Testing clamps???? I first go by use reports (not tests) from other woodworkers and then manufacturer specs (a very, very, very, distant second). It the clamp works like I think it should (jaws are easy to move, stay parallel, lock, don't slip, and provides enough force for sufficient glue squeeze out, etc., I keep it, if not I take it back.


Next, why do the metal pipe clamps also loose pressure, there is no jaw material to compress, its all metal to metal, right?

Whats your next theory ? :-)

What kind of clamps? Pipe clamps are notorious for slipping, the pawls often do not fully engage the pipe, especially when using galvanized pipe which is covered in very soft zinc. You can't convince me that they lose clamping force in a gauge-only test, unless the head slips or you are applying enough force to stretch the bar!

Theory? Isaac Newton and others would heartily disagree.

[Peter Quadarella]

First off, it is not clear or proven which is occurring - jaw deformation or slipping.

Secondly, if we suppose the jaw is being deformed (compressed), then that allows for more space between them causing less force to be exerted on the object. It is as simple as that. If someone used a 6" piece of styrofoam as a clamp pad, they would have to know that although they are sure not to marr the wood, it is not going to apply the same force in an hour as it does now. We can talk about the wood "pushing back" or being deformed itself, but what wood are we talking about? Basswood? Brazillian Cherry?

And it doesn't matter to me anyway; I don't think we are talking about absolutes, we are talking about relative results. Perhaps these results don't matter to you, or even most woodworkers, since clearly everyone is having no problem with glue lines and everyone has plenty of clamps. But it is useful information IMHO, and I thank Will for posting it. Hopefully you won't refrain from such helpful posts in the future.

Thanks.

[Steve Clardy]

Interesting thread. Took me a while to read through it.

Will. Have you tested and Jorgenson Cabinet Masters?
Have you tested their I-beam clamps? <---my preferred clamps.

[Will Blick]

> we are talking about absolutes, we are talking about relative results.


Yep, I could not say this enough times, and yet, somehow Alan does not comprehend this issue. The Stanley clamp pulls 20 - 30% more initial clamp force than the K's. The Stanleys holds 85% of its force over 4 hours, vs. 50% for the Besseys. Exact same test for both.... my conclusion... the Stanley out performs the Bessey, that's IT! Alan refused to accept this very simple premise....

why do I still buy K's? Cause I like the flexibility to join them together, I get em at a good price and I work around these shortcomings..... like everything, else, its all about trade-offs. But is nice to know what exactly the trade-offs are.... hence the value of the relative test.


> But it is useful information IMHO, and I thank Will for posting it. Hopefully you won't refrain from such helpful posts in the future.


Peter, I appreciate you mentioning this.... IMO, it's situations like this that keep people from sharing useful information. It's unfortunate, but its the nature of an open forum. I started this thread out by stating, I don't want this to turn into a "why so much pressure" and over analyzing the test. The test is on a level playing field for all clamps.... hence the value of the findings. But there is something about clamp pressure that brings out these never ending threads.....


Alan, I have tried my hardest to explain what appears so simple, but IMO you are turning a mole hill into a mountain, and this last post has demonstrated such. As a general rule, if I start a thread, I do my best to hang with it.... but we have limits.... I will try to address a few of your new points and hopefully we can call it quits....


1) As for the pad deforming being the culprit. It appears the picture of the clamp did not appear for you, not sure why, but if you can see from the pix, the gauge only takes up 1 sq in of surface are of the clamp pad. If all this loss of pressure came from pad deformation, then after 24 hrs of constantly re tightening, I would see some deformation in that 1 sq inch zone....yet, a Starett straight edge, toleranced to .0005" when placed against the pad, before and after the test..... you can NOT see day light through the straight edge.... the clamp pad material is this tough! No surprise, these type ww clamps have been around for 50+ the makers have had time to get it right.... If you can't grasp this, I have nothing more to add....


> the physical conditions must be identical- the means of applying force, measuring force, how much force, to what material, over what area, for how long, at what temperature, etc. etc.


Alan, its statements like this that lead me to beleive you are trying to prove your point, vs. accepting common sense. Same means of applying force, my same hand, which exerts within 10% the same pressue most any time... how do I know? I tested enough to know. Same temp, same shop, same testing gauge. I am not looking for 2% errors here, this is not a scientific test that I will produce publish for Govt. use. This test looks for large variance between clamps, so when I have a few hundred $ to spend on clamps, I buy the ones that make the most sense. Get it?


> So when you move the jaws of the clamp against an object that compresses, or if the jaws compress, and do not spring back with the same amount of force and distance as the strain gauge, then you see a reduction in applied force. That can occur almost instantly or over time.


Again, 80% of what you wrote, such as this above - misses the piont. There is no wood in the test, there is no reason to add a new variable, i am testing the clamp, not the wood. But more importantly, as other posters have correctly pointed out.... its the same test for all the clamps, so who gives a hoot about why one clamp looses pressure vs. another clamp...or why one clamp can only acheive 50% the initial force vs. another. Who cares? I don't plan to buy $25 clamps and disect them to get rid of their shorcomings..... I will just buy the ones that make the most sense.


> Testing clamps???? I first go by use reports (not tests) from other woodworkers and then manufacturer specs (a very, very, very, distant second).


Not many engineers would ever agree with this approach. First you scream the science is wrong in the test, now you scream, its best just to listen to other ww's, who have no reliable test data?? huh? Pick a side please...

I have meters for everything.... In some of my phtographic processes, people are so fooled by light levels, its crazy. I ask people how much brighter light source A is vs. light source B, often I hear comments like 20%, 10%.... and yet, its 80%. This is common, in many areas we are lousy at discerning differences without the aid of gauges or test aparatus. Clamps are no exception..... and my clamp tests did not vary much from the two magazines that ran similar tests....one of them had a phd in wood science....so its best you present your data to him, as he used the same pneumatic gauge I did.


Alan, admittedly, I am exhausted from this...... if you still disagree, just use the ancedotal data from different posts on the internet, and make your clamp purchase decisions from that data. It's best you disregard my erronous tests... OK?


It seems the pix are being viewed, so they must appear for some? I think this paste below might work....



http://i.pbase.com/o6/25/583725/1/103632192.lcah4n1R.Stanley4hrs.jpg




http://i.pbase.com/o6/25/583725/1/103632137.0R0LS1Gl.2k4hrs.jpg

[Steve Clardy]

Will. I cannot see any pics. No red X's, no links

I see red X's today.

[Will Blick]

these pix above are appearing on my screen.... no one else can see them ?

[Alan Schaffter]

First off, it is not clear or proven which is occurring - jaw deformation or slipping.

Secondly, if we suppose the jaw is being deformed (compressed), then that allows for more space between them causing less force to be exerted on the object. It is as simple as that. If someone used a 6" piece of styrofoam as a clamp pad, they would have to know that although they are sure not to marr the wood, it is not going to apply the same force in an hour as it does now. We can talk about the wood "pushing back" or being deformed itself, but what wood are we talking about? Basswood? Brazillian Cherry?

And it doesn't matter to me anyway; I don't think we are talking about absolutes, we are talking about relative results. Perhaps these results don't matter to you, or even most woodworkers, since clearly everyone is having no problem with glue lines and everyone has plenty of clamps. But it is useful information IMHO, and I thank Will for posting it. Hopefully you won't refrain from such helpful posts in the future.

Thanks.

In general, Peter, I agree.

Slippage could have been measured and verified by using a precision dial indicator or digital indicator as I mentioned earlier in this thread, once the conditions are such that no compression exists.

Will's error was to rely on a force gauge without taking into account the effects of compressibility. The force gauge's seemingly absolute and objective readings, unfortunately, are too affected by even the relatively minimal compressibility of the clamp jaw faces, but much more so by any compressible material being clamped. Force gauges are usually used with machinery, between surfaces that barely move once pressure has been applied and which are generally non-compressible. Though the Bessey polyamide jaw faces are impact and break resistant, they are compressible to the tip of or any pressure pad used with a force gauge.

To test and compare clamping pressure (by a particular person and between different clamps (not vs manufacturer's claims), and the clamps ability to maintain that pressure over time, Will needed to ensure there was no compressible material between the jaw faces and any force gauge and that there was or was not jaw slippage.

Correct bottom line- it really doesn't matter with proper clamping technique. Clamping force results do matter to me, but not those posted in this thread.

[Will Blick]

> The force gauge's seemingly absolute and objective readings, unfortunately, are too affected by even the relatively minimal compressibility of the clamp jaw faces,


I have addressed this at least 8x... and several other posters supported the "it's a relative test" at least 3x that I recall. You refuse to either read it or comprehend it.... not sure which....but its getting old....


> Though the Bessey polyamide jaw faces are impact and break resistant, they are compressible to the tip of or any pressure pad used with a force gauge.


have you tested this? I can not compress the poly, not with 1000 lbs of force and a small 1" sq surface metal contact area.... and as I mentioned, even if it did compress, it can't compress forever, and yet, as if what you suggest is true, when I constantly re tighten, eventually the poly would compress the poly till its near paper thin.... but of course that does not happens confirmed by a Starett straight edge...... but please Alan, don't let that fact alter your position....as your roots are way too deep to change, I fully understand....


More importantly.... a previous poster made an excellent observation about buying a product super charged :-), vs. one "on the edge." Clamps that reach higher initial clamping pressures have one nice advantage. Here is an extreme example....compare the Stanley and the lousy Gross Stabil Parallels... When I do a thin panel glue up, I need very little pressure, as the wood is thin, say 1/2" inch and maybe 24" long. I use about 400 lbs of pressure per clamp and about 5 clamps total.


With the Stanley clamps, 400 lbs is a breeze, I tighten them with my finger tips, no skin loss there. If I used the GS's I would be makin blisters trying to get those dogs to 400 lbs. This is a good example of why excessive capacity is not such a bad thing, even if you don't use it. It's just easier on your hands! All the knuckle bustin is done during the last 400 lbs of the clamps max. capacity.

This also is a glaring endorsement for bar clamps... they can hit 400 lbs with two fingers. Assuming the rear standards don't slip....

[Matthew Bradburn]

these pix above are appearing on my screen.... no one else can see them ?

I find the pix work fine both in firefox 3 and internet explorer 7. They want to open in a new window, maybe that's causing people grief.

[Alan Schaffter]

You finally got something right- the pic now shows.

As to your other efforts and analysis they continue to be flawed, as I have pointed out. I fully understand what you keep saying, but repeatedly (8 times or 100 times) conducting and describing the results of fundamentally flawed tests do not and will not make them them valid, no matter how much you wish it to be so. Your tests, unfortunately do not follow the scientific method and are not sound engineering, so are worthless as relative, comparative, or otherwise, results. Until you confirm or disprove whether the clamp head moves and by how much over time (either because it slips on the bar or because there is lashback in the leadscrew, etc.), measure the "relative" compressibility of the jaw faces of the different brands, and quantify the specifications and effects of compressibility or lashback movement on your force gauge, you are just wasting your time showing the face of the gauge or posting numbers. You are just arriving at flawed conclusions from flawed tests. There is a reason it is called Newton's "Third Law" not his third theory. You are not telling us anything useful or credible, relative or otherwise. Your testing involves a lot of bliss.

One third of what you see is in front of your eyes. Two-thirds is behind your eyes. Those who are not satisfied with the evidence already offered will not be convinced by any amount of further testimony—their skepticism is invincible.

Don't waste your time on a final shot, I won't waste my time on one, and will not reply. Good evening.

[Tim Put]

The goal of the test in question was to measure (approximately) the force that can be applied and maintained by the clamps. Besides you being wrong on numerous points of mechanics and physics; the property in question is force, Will used a force gauge. The relative incompressiblity of the force gauge (which you stated as a problem earlier) if anything makes the clamps job in maintaining initial force easier.

Might I ask, Alan, if you don't find a force gauge to be a suitable way to measure the force a clamp can apply, what would a suitable measurement apparatus look like?

[Chris Padilla]

I find the pix work fine both in firefox 3 and internet explorer 7. They want to open in a new window, maybe that's causing people grief.

Pics no worky for my IE 6.