2/4's and bolts for clamps

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Forum topic by athomas5009 posted 05-17-2015 06:57 AM 1006 views 0 times favorited 6 replies Add to Favorites Watch
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293 posts in 1041 days

05-17-2015 06:57 AM

Hey all I wanted to get some opinions on using 2×4’s and 3/8” bolts as clamps for face laminating large sheets of plywood before I do it. I need to replace my sons basketball back board with was previously a stationary pole and 3/4” plywood that came with the house. I looked around for a decent on and found out I could make one for have the price have a nice piece of birch ply left over all while paying for it with general funds instead of shop funds.

The old back board could have been stiffer so I figured 3/4 birch ply with a 1/4 oil hardboard front and back would take care of that. But then that left me with the problem of laminating (3) 54”x42” pieces of sheet goods together. I know the best way is glue and screws but I didn’t want to see the ugly screws everyday, plus I feel that all the counter sunk screws would allow the elements to deteriorate thing sooner. So I was heavily leaning towards glue only.

The problem with that is with out an industrial press the only ideal way is to use a an extra sheet of plywood on the front and back with lots of cauls. Well I wasn’t about to spend a Hundo on clamping plywood, so my plane was to just do it with plywood and cauls. But instead of playing teatertoter with clamps and cauls I figured making an easier to use reusable jig was the way to go. So I got a bunch of 2×4x12’s and cut them to 4/5 feet, drilled a hole and used a. Coarse 3/8’ hole. Do you think this would be sufficent clamping force. My thoughts are 6 sets of clamps/cauls plus 2 3-4 more in the opposite direction. I figured I would start the cauls 4” in and the every 8-10” and also tighten the edges with reg clamps. Hay anyone ever attempted this before?

For a finish I figured 3 coats oil varnish blend followed by 3 of wiping varnish. This way reapplication wouldn’t be to labor intensive down the road

-- Sometimes you're flush and sometimes you're bust, and when you're up, it's never as good as it seems, and when you're down, you never think you'll be up again, but life goes on.

6 replies so far

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Rick M.

7735 posts in 1804 days

#1 posted 05-17-2015 07:32 AM

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Combo Prof

2256 posts in 702 days

#2 posted 05-17-2015 11:18 AM

Are you actually make cauls or leaving two by fours flat. If cauls then yes your bolts will work.

Otherwise support the middle from below and put a bag of sand or a heavy weight in the middle and then lots of clamps/clips on the edges. Trim the hardboard to the plywood with a router flush bit . (I’d make the hardboard a bit over sized. It will slide on the glue.) seal the edges well when your done.

-- Don K, (Houghton, Michigan)

View Crank50's profile


170 posts in 1000 days

#3 posted 05-17-2015 03:07 PM

When you get it all lined up, before you apply clamp pressure, fire a few 23 gage pins into the sandwich to keep it from sliding around on the glue. Bolts with washers will work, but your 2×4 cauls will need the arc against the laminate like a purchased caul.

Can you really do this as cheaply as buying one ready made when you consider all the labor and fools/fixtures required?

View Andre's profile


993 posts in 1230 days

#4 posted 05-17-2015 03:19 PM

Point of interest, clamping pressure is directed at 45 degrees to the contact point! Clamping plywood together is like applying veneer, so unless the 2X4 s’ are touching each other may as well just toss a few sand bags on it as Rick suggested. The glue you use will be a big factor in final product.

-- Lifting one end of the plank.

View bigblockyeti's profile


3589 posts in 1145 days

#5 posted 05-18-2015 02:45 AM

Rick nailed it, bags of sand or some sort of barrier and gravel piled on top. Works out to be much more even clamping force and can get up into the tons pretty quick if you have sand or gravel or have access to some. I used to keep bags of lead shot around the shop for difficult clamping situations and have since used them for reloading, but it’s amazing how much a fairly small bag can weigh.

View athomas5009's profile


293 posts in 1041 days

#6 posted 05-18-2015 03:48 PM

The clamping cauls with bolts and clamps around the edges seemed to work well. I used 6 across the length spread out every 8 inches. Then I used 4 more on top of that in the opposite direction. I ended up using my table saw as the assembly table because it was the only flat surface large enough. I couldnt see much if any light between the cauls.

The only thing I’m a lil concerned about is whether I used enough glue. I rolled out a nice thick layer on the ply, prob around 12oz but as soon as I laid the hardboard on top it sucked it up quick I’ll have to check the strength of the edges before I do the other side. If I have any doubts I can always make that the back side and throw some screws in and fill with epoxy. After I already glued up that side I read some where that it’s good to put a thin layer of watered down glue on the hardboard first.

I wanted to try out the caul/bolt idea because I read some where that the really come in handy and there are a cpl workstation projects I have planned where they would help. With the sheet goods, 2×4s and bolts I have 100 or less in the project the cheapest I’ve seen a comparably backboard is 200.

-- Sometimes you're flush and sometimes you're bust, and when you're up, it's never as good as it seems, and when you're down, you never think you'll be up again, but life goes on.

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