Clamping Force For Glueup - Thick Tabletop - Woodworking Talk - Woodworkers Forum
 
Thread Tools Display Modes
post #1 of 11 Old 12-01-2014, 08:24 AM Thread Starter
Member
 
Join Date: Nov 2014
Posts: 43
View Stevebo's Photo Album My Photos
Clamping Force For Glueup - Thick Tabletop

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.
Stevebo is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 12-01-2014, 09:29 AM
Senior Member
 
Join Date: Sep 2011
Posts: 26,058
View Steve Neul's Photo Album My Photos
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.
Steve Neul is online now  
post #3 of 11 Old 12-01-2014, 10:17 AM
Senior Member
 
Join Date: Apr 2011
Posts: 139
View verdesardog's Photo Album My Photos
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.
verdesardog is offline  
Sponsored Links
Advertisement
 
post #4 of 11 Old 12-01-2014, 11:11 AM
Senior Member
 
BernieL's Avatar
 
Join Date: Oct 2011
Location: Greenville NH
Posts: 1,399
View BernieL's Photo Album My Photos
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.

Its' never hot or cold in New Hampshire... its' always seasonal.
BernieL is offline  
post #5 of 11 Old 12-01-2014, 01:12 PM
Senior Member
 
Join Date: Nov 2011
Location: Coastal NC
Posts: 1,160
View HowardAcheson's Photo Album My Photos
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

Howie..........
HowardAcheson is offline  
post #6 of 11 Old 12-01-2014, 01:16 PM
Wood Snob
 
Al B Thayer's Avatar
 
Join Date: Dec 2011
Posts: 5,963
View Al B Thayer's Photo Album My Photos
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


Al B Thayer is offline  
post #7 of 11 Old 12-01-2014, 01:48 PM
Sawdust Creator
 
ryan50hrl's Avatar
 
Join Date: Jun 2012
Posts: 8,047
View ryan50hrl's Photo Album My Photos
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.

The tools don't make the craftsman....
ryan50hrl is offline  
post #8 of 11 Old 12-01-2014, 02:30 PM
Village Idiot
 
epicfail48's Avatar
 
Join Date: Mar 2014
Location: Springfield MO
Posts: 4,941
View epicfail48's Photo Album My Photos
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

I need cheaper hobby
etsy.com/shop/projectepicfail
epicfail48 is online now  
post #9 of 11 Old 12-01-2014, 02:58 PM
Senior Member
 
Join Date: Jul 2008
Location: Florida Panhandle
Posts: 12,471
View GeorgeC's Photo Album My Photos
Quote:
Originally Posted by Steve Neul View Post
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
GeorgeC is offline  
post #10 of 11 Old 12-01-2014, 03:03 PM
Senior Member
 
Join Date: Jul 2008
Location: Florida Panhandle
Posts: 12,471
View GeorgeC's Photo Album My Photos
Quote:
Originally Posted by verdesardog View Post
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
GeorgeC is offline  
post #11 of 11 Old 12-01-2014, 03:06 PM
Senior Member
 
Lola Ranch's Avatar
 
Join Date: Mar 2010
Location: Central Washington State
Posts: 1,389
View Lola Ranch's Photo Album My Photos
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
Attached Images
   
Lola Ranch is offline  
The Following User Says Thank You to Lola Ranch For This Useful Post:
OnealWoodworking (12-01-2014)
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Woodworking Talk - Woodworkers Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Glueup jig for segmented turnings. Alchymist Tips, Tricks, & Homemade Jigs 1 09-08-2013 07:12 PM
1/4 Material GlueUp BASEBALL FAN Joinery 9 04-04-2012 04:55 PM
Air Force One trash collector Off Topic 5 01-23-2009 05:15 PM
Air Force One smitty1967 Off Topic 7 08-08-2008 08:45 AM
Segmented bowl glueup clamping coffeetime Woodturning 2 01-01-2008 06:50 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome