Maple glue up

  • Advertise with us

« back to Woodworking Skill Share forum

Forum topic by fladdy posted 03-01-2011 04:29 PM 1928 views 0 times favorited 8 replies Add to Favorites Watch
View fladdy's profile


93 posts in 3188 days

03-01-2011 04:29 PM

Topic tags/keywords: maple clamp

I just read an article on FWW website about wood glue up. In the article they use an equation to help suggest the number of clamps needed for a proper glue up. The equation is Surface area (sq. inches) x Recommended Clamping Pressure (maple is 600 for quartersawn, 1200 for flat sawn) divided by the strength of the clamps (1050 for 3/4” pipe clamps). This would mean that I would have to use 12-13 clamps just to glue up 24” long pieces of maple. Is it just me or is that a little excessive??

Here is the link to the articles:

-- Fladdy

8 replies so far

View Viktor's profile


466 posts in 3594 days

#1 posted 03-01-2011 06:27 PM

That article is nonsense (or an error). Compression strength for wood across the grain is approximately 4MPa (600psi) for pine and 7MPa (1000psi) for oak. Clamping pressure they recommend is around crushing point for wood.
Further from the article: “But joints clamped at the recommended levels will be quite strong enough, with the glueline being stronger than the wood itself”. The glueline will be stronger than wood itself even at 1/10 of the pressure they recommend. How did they determine “optimal” anyway?

View BobG's profile


172 posts in 3137 days

#2 posted 03-01-2011 06:35 PM

WOW! And I thought I had enough clamps! Hey honey where is that credit card I’m going to Rockler!

-- BobG, Lowell, Arkansas--------My goal in life is to be the kind of person my dog thinks I am! Make more saw dust!!

View richgreer's profile


4541 posts in 3250 days

#3 posted 03-01-2011 07:44 PM

This question has come up before on this forum. The consensus then was that the article was simply wrong.

If I were gluing up some maple that was 24” long, I would probably use 3-4 F-style clamps. In my opinion, that number of clamps just feels right.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View fladdy's profile


93 posts in 3188 days

#4 posted 03-01-2011 07:45 PM

Thanks for the feedback. I thought it was goofy myself.

-- Fladdy

View McKinneyMike's profile


80 posts in 2836 days

#5 posted 03-01-2011 07:55 PM

Clamps ever 6” is more than ample in my opinion.

-- McKinney Hardwood Lumber --Specializing in exotic and figured hardwood lumber -McKinney, TX

View childress's profile


841 posts in 3717 days

#6 posted 03-01-2011 09:19 PM

In my experience with gluing (which is on the high end for gluing simple edge and face joints) I’ve tried all different kinds of “clamping force” techniques to see the different outcomes. I’ve never had a glue joint failure with any. What I can say is that the most important aspect to getting a quality joint is to apply the clamps in the right position as FWW helped describe here. This, to me, is the key of laminating properly….

-- Childress Woodworks

View DLCW's profile


530 posts in 2830 days

#7 posted 03-02-2011 04:31 AM

IMHO if you clamp with that much pressure I would think you would squeeze all the glue out thus starving the joint. I only tighten clamps enough so I get a little bead of squeeze out and call it good. Never had a glue joint come apart or fail.

-- Don, Diamond Lake Custom Woodworks - - "If you make something idiot proof, all they do is make a better idiot"

View fussy's profile


980 posts in 3226 days

#8 posted 03-02-2011 08:36 AM

I believe in the very next issue they corrected that article saying what several of you opined; the preassure needed as given was nonsensense, and the clamp distribution was preferred. However,, Childress and DLCW have it right. Overtightening will starve the joint, and proper positionog of clamps is the critical factor. IN other words, they wuz right and FWW mostkly wrong, except where they were partly right. I’m going to bed now.


-- Steve in KY. 44 years so far with my lovely bride. Think I'll keep her.

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics