# Shop made screw clamps



## Adair (Mar 4, 2014)

Hello all, 

I was wondering if I the following idea would be effective. I am a beginning woodworker, and with my current project I need to laminate two 3/4 plywood shelves together. I planned on ripping the shelves down to 1/2" over their final size of 12-1/4", gluing them together (full 8'-0" length), then doing the final rips and crosscuts. 

I don't have nearly enough clamps to do the job, but I've got piles of doug fir studs and some all thread. I thought I could make clamps like what I've shown in the image below. Will they create enough pressure evenly over a 12" wide shelf if they were made out of 2x4s? How frequently should they be spaced? Could I stack more than one pair of glued shelves and expect to compress them enough? 
-Adair


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## ryan50hrl (Jun 30, 2012)

You would need to use the 2x4's on edge, and get the screws as close to the edge of your glue up as possible. If the bolt is a bit from the edge, you rapidly loose clamping force in the middle as the 2x4 bows


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## mobilepaul (Nov 8, 2012)

Adair said:


> Hello all,
> 
> I was wondering if I the following idea would be effective. I am a beginning woodworker, and with my current project I need to laminate two 3/4 plywood shelves together. I planned on ripping the shelves down to 1/2" over their final size of 12-1/4", gluing them together (full 8'-0" length), then doing the final rips and crosscuts.
> 
> ...


This info may help you with your dilemma, all you would have to do different is drill, or however best works for you, the edges of your board in a slot fashion to allow for a little wiggle room

http://www.highlandwoodworking.com/woodnews/2010april/cauls.html


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## Miller Woodworks (Dec 11, 2013)

Do you have anything heavy? You could just put some cinder blocks or cans of paint, or just about anything heavy on the plywood to "clamp" it down. As long as you get a good glue coat, you should be fine. I've glued plywood together before and just laid it down on the concrete floor and put various heavy items on it for clamps. Instead of going through the trouble of building a clamping system for it, try just using weights.


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## Steve Neul (Sep 2, 2011)

If the boards had a gentle curve to them where you placed the crown toward piece being clamped it would work. The curve would compensate for the bowing you would get when tightening it.


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## Manuka Jock (Jun 27, 2011)

I reckon yep make them .
You will use them again for other projects .

As Ryan says , use the timbers on their edge . 

And as we know , straight wood doesn't always stay straight ,
so always lay them with the Bottom one with the round Up and the Top one with the round Down .
Opposing rockers as it were .
That way there will not be an air/glue pocket trapped inside the lamination.


Do Not lay both 'rockers' the same way , you will end up with a glue-laminated * cupped* plywood shelf.


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## rrich (Jun 24, 2009)

You're going to wrap the wood clamping bars with clear plastic packing tape anyway. (The squeeze out wont stick.) In the center, under the tape about an inch wide just add 6 layers of playing cards.


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## builder64 (Jan 1, 2014)

Another idea is to make it over-sized and staple or screw the perimeter (being sure to mark a line so you avoid putting fasteners on your cut lines). If the boards are cupped, put the cupped side in on both pieces so the perimeter has a gap all the way around when you stack them for a dry fit. After it's dry, you can rip off the stapled/screwed part.

12" is pretty narrow, so if you are going to use cauls, I would go lengthwise. If you use a bunch of clamps like in your picture, your piece may still be bowed or, more likely, wavy, when it's all finished. 
You could use your idea in combination with lengthwise 2x4s (2-3 on top, 2-3 on bottom). Lay everything out except your top 2x4s and top clamps, and glue up right on your jig.

To answer your question: yes, you can glue up more than one pair of pieces at a time, especially if you are just stacking them.


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## Adair (Mar 4, 2014)

Cauls, so that is what they are called. That link was great and extremely informative. I'll definitely be making some of those. 

For the shelves, I realized that I have lots of very heavy things around the shop (Thanks you Miller Woodworks for the idea) I have a cast iron table from an old milling machine that probably weights 1,000 pounds. I could make my own platten press with little bottle jacks in the corners and get a nice, even force. 

Thanks all! 

-Adair


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## Manuka Jock (Jun 27, 2011)

Adair said:


> Cauls, so that is what they are called. That link was great and extremely informative. I'll definitely be making some of those.
> 
> For the shelves, I realized that I have lots of very heavy things around the shop (Thanks you Miller Woodworks for the idea) I have a cast iron table from an old milling machine that probably weights 1,000 pounds. I could make my own platten press with little bottle jacks in the corners and get a nice, even force.
> 
> ...


 We gotta see pics of that :yes:


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## Al B Thayer (Dec 10, 2011)

Adair said:


> Hello all,
> 
> I was wondering if I the following idea would be effective. I am a beginning woodworker, and with my current project I need to laminate two 3/4 plywood shelves together. I planned on ripping the shelves down to 1/2" over their final size of 12-1/4", gluing them together (full 8'-0" length), then doing the final rips and crosscuts.
> 
> ...


You might, if possible lay them against each other and put the crown faces together, if there is any, so the boards would only need clamping on the edges. You could also remove a very small amount on the edges to accomplish the same thing. 

This type of glue up will produce a very strong joint even if done poorly. Since its plywood. your not going to need a lot of clamping pressure. 

Also take into account how you set the glue up to dry. If it doesn't lay flat after clamping. That would be a good time to make corrective measures.

Al

Nails only hold themselves.


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## woodnthings (Jan 24, 2009)

*as I said previously, this is a big project*

Big projects require a different mindset when "multiples" of anything need to be constructed. Everyone is thinking glue and clamps and weights .... I'm thinkin' contact cement, no clamps just "smack" them together, apply some pressure and go on to the next unit. 

Now the question is will contact cement work well on 2 pieces of 3/4' plywood? I don't know for certain, but I don't see why not. It certainly works well enough for "thin to thick" as in countertop laminates. Why not "thick to thick"? Maybe someone knows?

I do know that the correct application and set up time would be critical. So that's my suggestion as it would speed up construction and require less tooling in the form of clamps.

http://www.ehow.com/how_7654273_use-glue-sheets-plywood-together.html

http://joneakes.com/jons-fixit-database/2165-Working-with-Contact-Cement


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## Al B Thayer (Dec 10, 2011)

Wooden
That would probably work if the plywood wasn't the kind where the veneer wasn't glued to a layer of paper. The walnut plywood I'm working with is like that. Not sure what it's called.

If I was gluing it. It would only require a few clamps. 

Al

Nails only hold themselves.


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## Adair (Mar 4, 2014)

Well this is about as innovative as I got. The big cast iron platten was too cumbersom, but this piece of square tube was just right. I filled it with scrap metal and anything I had lying around. I probably have 800 lbs of dead weight. It does a good job of squeezing out the glue. I slung it from the steel overhead with a chainfall. I can only get to three shelves quickly enough before I feel I have to put the weight on. I need a glue helper. Thanks for all the tips. 

[/URL


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## BassBlaster (Nov 21, 2010)

Wow, all you really needed was some cinder blocks or something. Id be concerned now that you squeezed out too much of the glue.


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## Bleedinblue (Mar 4, 2014)

Lol, holy definition of overkill!


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## Manuka Jock (Jun 27, 2011)

:icon_smile: man that's some wood press .
I would have just bought thicker ply


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## Adair (Mar 4, 2014)

Really, overkill? That's only 2.2 PSI. I didn't think that was overkill. It definitely doesn't squeeze out too much glue. I've read that 10-15 PSI is often called for in a vaccuum press. Tightbond recommends 100-150 PSI for softwoods. Plus, I've got a stack of six boards in there resisting slight deformation. A couple of CMU blocks wouldn't compress all of that. The setup took me twenty minutes to put together. I often go overkill, but I never would have thought that I did with this press.


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## laadams85 (Mar 21, 2014)

This article suggests some crazy high pressures for gluing up woods. I think you'll be fine.

Glue Clamping Pressure


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