Newbie again quick question

• posted on February 18, 2004, 2:49 am
When gluing boards together is pressure necessary? In other words HOW much should I tighten my pipe clamps?
Rich I know this question sounds dumb to you guys but hey I'm just learning
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• posted on February 18, 2004, 2:58 am
In rec.woodworking

Yes it is. Each glue has a manufacturer recommended clamping pressure. Usually is is around 175-250 psi for hardwoods. Read more here:
http://www.titebond.com/IntroPageTB.ASP?UserType=1&ProdSel=ProductCategoryTB.asp?prodcat=1
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• posted on February 18, 2004, 3:23 am
In rec.woodworking snipped-for-privacy@nospam.com (Bruce) wrote:

I realized I didn't answer your question of "how much" I doubt many have actually calculated their clamping pressures as that would be a real pain in the ass to do. You'd have to calculate surface area of the clamped area, divide by the number of clamps, torque each clamp to a known value and perform the math to figure out how much linear force is applied by the screw when twisted with a particular torque.
Hmmmm...
Clamping 2 boards, 1' square how many twist grip bar clamps?
144 square inches so to get 200 psi you need:
200 * 144 = 28,800lbs of total clamp pressure
28,800 / 1000 lbs** per clamp is 29 clamps!! What the hell? Is something wrong with my math? I'd put about 4-6 clamps on that myself. I think you better break out the C-Clamps.
**From the Bessey website, 1000 nominal clamping on their heavy bar clamps. The way I see that, you can figure 1 clamp per 5 square inches.
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• posted on February 18, 2004, 3:27 am
I normally just tighten enough to not squeeze out all the glue, but enough to squeeze out a bit. Don't tighten till the handle stops, but till it gives good resistance. That's how I do it with Elmer's Yeller glue.
KY
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"Bruce" < snipped-for-privacy@nospam.com> wrote in message
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• posted on February 18, 2004, 5:49 am
Bruce wrote:

By that link to attach a 32" oak face frame to 3/4" ply partition the minimum force needed is 4800 pounds. Roughly the weight of my truck. On one stile of a face frame.
Somehow I think many here have gotten away with less.
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Mark

N.E. Ohio
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• posted on February 18, 2004, 3:46 pm
brought forth from the murky depths:

That's seems higher, but it's just 200psi. Each clamp is capable of exerting many tons of pressure. My crank pressure method is thumb and little finger.

Indubitably. Glue is great stuff.
---=====--- After all else fails, read the instructions. ---=====--- Website Design and Update http://www.diversify.com
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• posted on February 19, 2004, 1:08 am
Larry Jaques wrote:

Just trying to create the visual of a 4wd teetering on a skinny slat and partition while the glue set.
And that was the low side of the recommended pressure for hard wood.

Doesn't take much.
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Mark

N.E. Ohio
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• posted on February 18, 2004, 4:29 pm
A vacuum bag only puts out about 14 psi. We glue with a leak (about 7psi) so as not to starve the joint for glue.
wrote:

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• posted on February 18, 2004, 3:30 am
The simple answer would be tight enough that the pieces do not slip apart from each other while the glue dries. Snug but not real tight.

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• posted on February 18, 2004, 4:01 am
Great, I am one of the ones who go thought you had to go nuclear on the pressure.
Again I applaud the fast responses Thanks again Rich
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• posted on February 18, 2004, 12:51 pm
wrote:

"squeeze-out"...no more. It's not advantagious to apply excessive pressure during a glue up. The mathematician and his calcs. are OT in this room.
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• posted on February 18, 2004, 1:27 pm

If you do that, you practically guarantee a glue-starved joint. You won't get a feel for it until you do a few glueups, but you want to apply just enough pressure to get a uniform bead of squeezeout. If you get the pressure right, once the glue has dried, the clamps will be slightly loose.
If you have to crank down on the clamps to close the joint, you need to re-do the joint.
Chuck Vance