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Clamps: how tight?

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Forum topic by Brett posted 07-11-2012 02:08 PM 2119 views 1 time favorited 21 replies Add to Favorites Watch
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Brett

636 posts in 1438 days


07-11-2012 02:08 PM

When I use clamps to hold boards together while glue dries, should I snug up the clamps just enough to keep the boards from sliding around, or should I tighten the clamps until the skin on my palm rips off and the blood vessels in my forehead burst? (Hyperbole, obviously—but a serious question.)

-- More tools, fewer machines.


21 replies so far

View Gregn's profile

Gregn

1642 posts in 1738 days


#1 posted 07-11-2012 02:14 PM

I only tighten my clamps till I have a slight squeeze out of glue.

-- I don't make mistakes, I have great learning lessons, Greg

View Knothead62's profile

Knothead62

2364 posts in 1716 days


#2 posted 07-11-2012 02:16 PM

What Gregn said.

View Sawkerf's profile

Sawkerf

1730 posts in 1823 days


#3 posted 07-11-2012 02:42 PM

Just tight enough to close any gaps and get fairly even glue squeeze out. Squeeze out happens when the wood surfaces make contact and the glue has nowhere to go. When you see it, you’re boards are where they need to be.

If you’re having to “grind” the clamps to close gaps, you need to improve your edge joining methods.

Just for grins once, I took two pieces of scrap that went together with an almost invisible joint and glued them together with no clamps. I just squeezed them together with my fingers, laid them down and left them overnight. The next morning, they were as solid as a clamped joint.

-- Adversity doesn't build character...................it reveals it.

View Fuzzy's profile

Fuzzy

293 posts in 2743 days


#4 posted 07-11-2012 02:43 PM

I use Besseys’ & Jorgies … I tighten them by hand, as much as possible … some will say that starves the joint of glue … others have PROVEN that to not be possible using only human hand strength. Most glue manufacturers (at least quietly) agree that more pressure is better, but they hesitate to make that recommendation, because some folks would just go nuts. Basically, with tools & clamps available in all but the most elaborate shops, it is not possible to over tighten your clamps, and the thinner the glue line, the better.

-- - dabbling in sarcasm is foolish … if you’re not proficient at it, you end up looking stupid … ... ...

View David Kirtley's profile

David Kirtley

1285 posts in 1753 days


#5 posted 07-11-2012 03:59 PM

Depends on the type of glue. Each will have it’s own recommendations.

-- Woodworking shouldn't cost a fortune: http://lowbudgetwoodworker.blogspot.com/

View Loren's profile

Loren

7832 posts in 2403 days


#6 posted 07-11-2012 04:26 PM

How much pressure depends on the beam strength of the
boards you are gluing together. I have K-body clamps I
use and I crank them pretty hard. I bet most seasoned
woodworkers do as well.

Sometimes if the clamp is tightened real hard you won’t
be able to loosen it with your hands and I’ve used pliers,
which scars up the handle. I have also drilled the handles
of some of my clamps to stick a screwdriver through it
to apply pressure and/or loosen a tight clamp.

-- http://lawoodworking.com

View TCCcabinetmaker's profile

TCCcabinetmaker

925 posts in 1110 days


#7 posted 07-11-2012 04:29 PM

they call it tightening the clamps for a reason, tight, this will help make sure you have a solid board to board joint where the glue is in the wood, not a strange kind of glue weld where the glue fills the gap. Though you need not bust blood veins.

-- The mark of a good carpenter is not how few mistakes he makes, but rather how well he fixes them.

View pintodeluxe's profile

pintodeluxe

3580 posts in 1568 days


#8 posted 07-11-2012 05:48 PM

I tighten them until the gaps are closed. With freshly jointed lumber and good pipe clamps, that is usually just good and snug.
In other words stop after your fingers blanch slightly, but before a pre-frontal anuerism.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View KenBry's profile

KenBry

449 posts in 1202 days


#9 posted 07-11-2012 06:24 PM

Tight enough to close all gaps but not so tight that the excess preassure creates new gaps. Allot does depend on the type clamp you are using as well. Use caution in clamping pressure too. You can over due it and destroy a clamp.

-- Ken, USAF MSgt, Ret.

View HoosierDude's profile

HoosierDude

48 posts in 1770 days


#10 posted 07-11-2012 06:28 PM

Here’s information from Titebond’s Product and Application Technical Guide:

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

I used to clamp the heck out of everything, just shy or bleeding hands and ruptured blood vessels. That was before I had a decent table saw and/or jointer.

Now that I understand the virtue of a joint that lines up without gaps before clamping, I tighten until I have uniform squeeze out. Either way, I’ve never had a joint fail.

-- Paul Lyons

View Bill White's profile

Bill White

3590 posts in 2715 days


#11 posted 07-11-2012 06:29 PM

Not so tight that ya have blood explode from your eyes. ( I couldn’t resist.)
Just get an even “squeeze-out” with PVA glues.
Bill

-- bill@magraphics.us

View MonteCristo's profile

MonteCristo

2098 posts in 943 days


#12 posted 07-11-2012 06:43 PM

My understanding is that you can’t make them too tight by hand. But I also agree that if you have to squeeze like crazy to close gaps, you need to re-joint.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View Enoelf's profile

Enoelf

192 posts in 1018 days


#13 posted 07-11-2012 07:55 PM

I agree with the suggestion of tightening to achieve a uniform squeeze out of glue.
I remember watching a woodworking video where the presenter showed that with a properly jointed edge, you can actually create a strong bond between two boards with just water. If your edges are clean, crisp, and smooth, it shouldn’t be necessary to burst any blood vessels or remove any skin.

-- Central Ohio, Still got 9 and 15/16 fingers!

View Loren's profile

Loren

7832 posts in 2403 days


#14 posted 07-11-2012 08:06 PM

It is true that if you joint your boards perfectly the boards can
just be glued and rubbed together to spread the glue. This
is an old method used in Japan and I’m sure many other places.

The old glues may leave less of a glue line though and of course
good clamping makes the glue line quite thin and even less
noticeable.

-- http://lawoodworking.com

View dnick's profile

dnick

952 posts in 1137 days


#15 posted 07-12-2012 03:40 AM

It’s pretty much like everything else in woodworking, you just develope a feel for it. Over time you learn from trial & error, you develope a rythum, a feel for what works. You can learn volumns from others, as I have, but the best teacher is your own experiance. Pactice, practice, practice. The most difficult part of woodworking for me, was & is, patience. Learn from everything you do.

-- dnick, North Hollywood, Ca.

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