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Clamping Pressure

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Forum topic by dustbunny posted 09-13-2009 02:13 PM 2547 views 2 times favorited 34 replies Add to Favorites Watch
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dustbunny

1149 posts in 1982 days


09-13-2009 02:13 PM

Topic tags/keywords: question clamp pressure gluing

I was reading in one of the woodworking magazines that too much clamping pressure can cause a glue starved joint. I read through the article twice and it gave no tips on how much pressure should be applied.

I have been noticing that some of my cutting boards are lacking a solid glue line. I kept saying to myself, ” I had plenty of squeeze out what happened?”

I have to admit my forearms are like bowling pins and my biceps don’t fit in girly style shirt sleeves. With that said I think I have been brut forcing my clamps and starving my joints. The more spotty the glue, the tighter I clamp up the next board. DUH !

So my question is this-

How much pressure is the right pressure? How do I know when to stop applying pressure? Should I purchase a torque wrench to tighten my clamps? LOL

Lisa

-- Imagination rules the world. ~ Napoleon Bonaparte ~ http://quiltedwood.com


34 replies so far

View Chris Wright's profile

Chris Wright

534 posts in 2168 days


#1 posted 09-13-2009 02:32 PM

Sadly there’s no real way to know exactly how much pressure you’re applying. What I usually do is tighten the clamps until I get a an even amount of squeeze out along the joint. Not very scientific, I know, but I’ve had some good joints that way.

-- "At its best, life is completely unpredictable." - Christopher Walken

View Walnut_Weasel's profile

Walnut_Weasel

360 posts in 1909 days


#2 posted 09-13-2009 02:37 PM

Interesting – I did not know you could over-clamp.

-- James - www.walnutweasel.wordpress.com

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oakdust

177 posts in 2502 days


#3 posted 09-13-2009 02:54 PM

Hummmm, is that why the treads on my clamps a strpped? lol

-- Bob, Rockford IL,

View CharlieM1958's profile

CharlieM1958

15706 posts in 2905 days


#4 posted 09-13-2009 03:40 PM

The rule of thumb I’ve always heard is just enough pressure to close the joint. If you are edge-gluing two perfectly jointed boards, in theory, very little pressure is necessary. You are really only holding the boards in place till the glue sets up.

-- Charlie M. "Woodworking - patience = firewood"

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Julian

880 posts in 2212 days


#5 posted 09-13-2009 03:52 PM

I have learned that just tightening the clamps till there is an even squeeze out works as previously stated. When overtightening the clamps, the joint will not be as strong.

-- Julian, Park Forest, IL

View a1Jim's profile

a1Jim

112299 posts in 2264 days


#6 posted 09-13-2009 07:55 PM

I’ve read a couple articles that tested wood joints saying they could not get a weakened joint from glue starvation not matter how hard it was clamped.

-- http://artisticwoodstudio.com Custom furniture

View degoose's profile

degoose

7038 posts in 2041 days


#7 posted 09-13-2009 10:34 PM

I only tighten the clamp until i feel resistance in the clamp screw. Then I check that I have uniform squeeze out.

-- Drink twice... and don't bother to cut... @ lazylarrywoodworks.com.au For lovers of all things timber...

View jack1's profile

jack1

1939 posts in 2714 days


#8 posted 09-13-2009 11:06 PM

I use Tite Bond glues, and they specifically say clamp for X amount to time and do not clamp overnight. l also look for a little squeeze out and have had no problems. In fact, I once tried to take apart a joint after an hour or so (miss matched board) and could only crack the wood near the joint. The joint went with one piece…

-- jack -- ...measure once, curse twice!

View Rick  Dennington's profile (online now)

Rick Dennington

3468 posts in 1881 days


#9 posted 09-14-2009 12:58 AM

Hey jack1—- I’ve used Tite Bond for years and years, but I don’t remember reading anywhere where it says not to overclamp at night—did I miss something somewhere on the label?
I’ve done dozens of furniture pieces, and had to let the glue dry overnight. No harm done to the piece that I could see. Rick D.

-- " I started with nothing, and I've still got most of it left".......

View dustbunny's profile

dustbunny

1149 posts in 1982 days


#10 posted 09-14-2009 01:08 AM

Thanks to everyone for responding. Great info and very helpful.
I think I have to break the bad habit of using my gorilla grip when clamping.

An addendum question -
As many of you pointed out, you look for uniform squeeze out.
What if you don’t get “uniform” squeeze out ? Do you take the joint apart and re glue ?

The problem is that some of my boards look fine, I can see a fine glue line along the joints, but then when I sand the board and finish with mineral oil (sometimes days to weeks after gluing) the glue line develops gaps like there were bubbles or something. This is why I think the joints are starved. I’ll try to get a picture loaded.

Lisa

-- Imagination rules the world. ~ Napoleon Bonaparte ~ http://quiltedwood.com

View SnowyRiver's profile

SnowyRiver

51450 posts in 2167 days


#11 posted 09-14-2009 01:58 AM

I always put clamp pressure on untill its snug…how much pressure that is I am not sure, but I dont crank hard on the clamps.

-- Wayne - Plymouth MN

View scrappy's profile

scrappy

3505 posts in 2117 days


#12 posted 09-14-2009 02:42 AM

Allway thought you had to go tight as possible. Then found about “Tapeing” miter corners to hold for glueing. Not near as tight as the clamps and still works great.

-- Scrap Wood's the best...the projects are smaller, and so is the mess!

View BeeJay's profile

BeeJay

71 posts in 1874 days


#13 posted 09-14-2009 03:13 AM

No, don’t pull it apart if it isn’t perfect, only if there is a pronounced gap. But to save any real concern, make sure you have a nice even coat of glue to start with and rub the board edges back and forth lightly. The oil problem could be because you haven’t cleaned it up properly. Always, where possible, clean up any excess glues while it is still wet. Some say do Some say don’t. I do and have had no problems up to now.

-- If you try to fail and succeed, what have you done?

View poroskywood's profile

poroskywood

614 posts in 2051 days


#14 posted 09-14-2009 03:15 AM

It’s just so hard not to tighten the snot out of that clamp. I was guilty of this but have changed my ways. Having well jointed material is the key so you don’t have to force things together. Excellent advice in this post!

-- There's many a slip betwixt a cup and a lip.--Scott

View Ken90712's profile

Ken90712

15082 posts in 1875 days


#15 posted 09-15-2009 11:41 AM

Very helpful to all of you. Being I have been in Aircraft Mx for 25 yrs, over kill has been beaten in to me. Everything I do at home weather remolding our house or a project in the woodshop, I apply over kill. I broke one of the rockler Alum. clamps the other day tighting it down to much. Opps. The Jet clamps that are on sale 1/2 off are amazing!
Ken

-- Ken, "Everyday above ground is a good day!"

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