Advise on making flat tops

[Jim Colombo]

I'm making a top (30" wide x 7' long) from 4" wide poplar lumber.

What would be the best way to keep it flat during glue up? No biscuits or other joinery, just glue.

Thanks,
Jim

[Bill Adamsen]

I'd use the extra two inches of material to make sure the edges were very square to the face. Then, since you have at least forty-nine feet of glue to apply (perhaps double) you might consider (depending on type of glue used) gluing it up in sections. Lots of balanced clamps protected from squeeze-out. Let us know what you decide to do, and how it works out!

[Jim Becker]

Keeping something flat while gluing up can be accomplished by doing it in steps (2-3 boards at a time) and using cauls. Clamps alone sometimes tends to "force a bend" if you inadvertently over tighten them and the cauls will keep things flat. The best cauls for this have a slight bow in the middle (convex toward the workpiece) which exerts force toward the middle of the assembly and forces things flat to the clamps. A commercial product is the BowClamp, which I use, but many folks create their own. But even flat, sturdy boards will do the job, too. Just be sure to use some wax paper or plastic wrap in insure the cauls don't get glued to your workpiece via squeeze out.

[Jamie Buxton]

Get your edges right. Do you have a jointer?

[Bill Carey]

2nd the use of cauls and gluing up in sections. And plain old package tape works great to keep the cauls from being glued to the work. Here's a pic of the QSWO top I just glued up.
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Another thing I recommend is making a couple of bench top horses - makes it much easier to put clamps on both sided of the work. These have dowels that go into the dog holes on my benchtop.
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Good luck. And do a dry run so you know you have the clamps you need, and the order that you are going to work in.

[michael langman]

I like your benchtop horses Bill. Thanks for posting them.

[David Eisenhauer]

Thanks for the bench-top-horses-that-can-fit-into-dog-holes tip Bill. I usually either end up cobbling/stacking some scrap together or fighting the clamps. Time for some horses I believe.

To the OP: Cauls are the way to go. You can run a search for how to make some without lots of work and then keep them on hand for future use. Be sure to mark them so that they won't get cut up later on. I believe that I have four sets made from some tubafors. I used a hand plane to create mine and that technique should show up in a search. I also am to lazy to fight glueing up many boards at a time to create a table top. Two-three at a time does me and I usually end up with two halves to glue together for the final glue up. If at all possible, final thickness planning can be done at the stages of the max width of your power planer for your sub pieces (like two 12" wide pieces, plus a final 6" piece for the final glue up) - all three pieces pre planned to remove minor inconsistencies in alignment. If only using a hand plane, then you have more options for final thicknessing.

[Bill Carey]

Thx. But I have to admit that they were pure serendipity. I made an island for the kitchen and SWMBO wanted a skirt that covered the wheels. Put it all together and called the inspector who wanted to know how she could lock the wheels! Off came the skirt and the horses were born.

[David Eisenhauer]

I was not going to say a word but I knew mine are not going to look as "colonial" styled (is that even a style?) or something similar. Now I understand. Whatever works and kudos on your serendipity that I am going to shamelessly rob. Thanks.

[Peter Quinn]

I make plywood t's out of two 4" rips of plywood long enough to exceed the top on both edges, lets me get clamps under and over. You can run stopped splines in easily with a router and 1/4" slot cutter as an alignment aid if required, works better than biscuits if the stock isn't straight and you dont have the thickness to sand/plane much. Cauls with clear packing tape helps keep the overall width flat and not curling up at the edges, as does the alternating clamps. It helps to have helper on wide tops for placing clamps, I always save a few 1/4" strips to run the length of the top and keep any metal out of the glue line to avoid staining the wood. A good dead blow hammer can help make localized adjustments where alignment isn't perfect. A wide belt sander is a godsend, when thats not available I do glue ups that fit in my planer, so a 45" wide table would involve just two joints to glue and flush by hand with belt sander and card scraper/hand planes.

[Bill Carey]

Have at it David. BTW I covered them with package tape to keep them from becoming part of the work.

[Jared Sankovich]

Curved cauls.

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