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Maple glue up

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Forum topic by fladdy posted 1242 days ago 1171 views 0 times favorited 8 replies Add to Favorites Watch
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fladdy

74 posts in 1612 days


1242 days ago

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:
http://www.finewoodworking.com/item/27121/how-to-glue-up-joints-different-woods-need-different-clamping-pressure#comments

-- Fladdy


8 replies so far

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Viktor

447 posts in 2018 days


#1 posted 1242 days ago

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?

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BobG

172 posts in 1561 days


#2 posted 1242 days ago

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!!

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richgreer

4522 posts in 1673 days


#3 posted 1242 days ago

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.

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fladdy

74 posts in 1612 days


#4 posted 1242 days ago

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

-- Fladdy

View McKinneyMike's profile

McKinneyMike

79 posts in 1260 days


#5 posted 1242 days ago

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

-- McKinney Hardwood Lumber --Specializing in exotic and figured hardwood lumber http://www.mckinneyhardwoods.com -McKinney, TX

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childress

841 posts in 2141 days


#6 posted 1242 days ago

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

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DLCW

522 posts in 1253 days


#7 posted 1242 days ago

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 - http://www.dlwoodworks.com - "If you make something idiot proof, all they do is make a better idiot"

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fussy

980 posts in 1650 days


#8 posted 1242 days ago

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

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

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