# Clamping Force For Glueup - Thick Tabletop



## Stevebo (Nov 11, 2014)

I'm working on a table top that's about 3" thick Cherry by 4' long.

From what I can tell the recommended clamping force for a glueup should be between 175 and 500 PSI (from varying sources)

175-250 PSI for hardwoods
250-500 PSI for cherry

Given the thickness of the table top I'm working on that would require a clamping force of between 25,000 pounds and 72,000 pounds.

This seems like a HUGE load.

Are these pressures intended for small area gluing jobs and don't scale well to large gluing areas or will I have to make myself some sort of clamping apparatus? 

Currently I have 4 x 1600# clamps available - about 6400# - between 9% and 25% of what I apparently need.


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## Steve Neul (Sep 2, 2011)

You don't really work by PSI. The joint should be fitted as such that it doesn't take very much pressure to clamp it up. If you are having to force the joint together then the joint is under pressure to come apart after it is done. Also with excessive pressure you can squeeze too much glue out making the joint weaker.


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## verdesardog (Apr 2, 2011)

According to an old article by "finewoodworking" there is no way to starve a joint by using too much force. If your boards are straight and true all the force you need is what it takes to keep them snug.


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## BernieL (Oct 28, 2011)

I read another post on this same topic a while back and one poster stated he didn't use clamps. As stated above - a snug fit is all I apply in your situation. As for joinery, the same rule of thumb for a well cut joint. Just make sure your boards meet with no space or daylight shining through.


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## HowardAcheson (Nov 25, 2011)

Here is the recommended clamp pressure from the folks at Titebond.

Quote
Appropriate clamp pressure is essential for a successful bond. We recommend
the following guidelines:
For softwoods (pine, poplar): 100-150 psi
For medium density woods (cherry, soft maple): 150-200 psi
For hardwoods (oak, birch): 200-300 psi
Clamp time is dependent on wood species, moisture content and environmental


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## Al B Thayer (Dec 10, 2011)

I'm with Bernie and Neul. Far better to take the time fitting before glue up. I start with very light pressure to keep the boards in place. Then after all the clamps are applied, the glue will hold the pieces from slipping while I tighten the clamps. Still I only use the needed amount. Try to remain calm and not worry about speed. Unruley boards get a whack with a hammer on a flat board.

Al


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## ryan50hrl (Jun 30, 2012)

Good fitting boards require far less force than poor fitting boards, but that said the glue manufacturers recommendations are the ideal situation. Most parallel bar clamps have the ability to produce around 1500 lbs of clamping force. Not having the ideal pressures doesn't mean you won't have a strong joint, it just means it could be stronger.


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## epicfail48 (Mar 27, 2014)

I've never bothered checking psi numbers for glueups. Way I do it is assuming a properly edge jointed board, with a good amount of glue, I apply pressure until I see little beads of glue squeezing put out


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## GeorgeC (Jul 30, 2008)

Steve Neul said:


> You don't really work by PSI. The joint should be fitted as such that it doesn't take very much pressure to clamp it up. If you are having to force the joint together then the joint is under pressure to come apart after it is done. Also with excessive pressure you can squeeze too much glue out making the joint weaker.


Well said!!!

George


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## GeorgeC (Jul 30, 2008)

verdesardog said:


> According to an old article by "finewoodworking" there is no way to starve a joint by using too much force. If your boards are straight and true all the force you need is what it takes to keep them snug.


I (and many others) disagree with "finewoodworking." In my early days of woodworking I did starve one or more joints, which later failed.

Up to 300psi is really not a lot of pressure. You can do that by hand without the advantage of mechanical assistance.

George


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## Lola Ranch (Mar 22, 2010)

*common sense could apply*

I am assuming we are talking about "Titebond" or similar type glues.

I regulate the clamping pressure according to the size of what I am clamping. On small things such as rings for a segmented turning, I'll spread the glue evenly on the workpieces and then simply hold the pieces together for about 10-15 seconds then carefully release it and move on to the next one. On a larger project such as glueing planks together for a table top, I use Jorgenson "I" bar clamp (Heavy Duty) and apply a fair amount of pressure. With a table top it is also important to alternate the clamps top an bottom and do not over-tighten to the point where you are warping or bowing the table top. Its also a good idea to use culls on the edges to prevent crushing the edges of your workpieces.

For joinery, I apply enough clamp pressure to draw the joint up snug and then stop so as not to cause crushing or twisting.

When doing curve laminated pieces, I use as much pressure as I am able to in an effort to squeese all the gaps out.

For those of you who do not need to clamp anything because your joinery is so perfect, congratulations, you have reached a level of craftsmanship that I have yet to acheive.

Bret


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