Can you edge glue plywood?

[Dave Anthony]

We're all familiar with gluing up narrow pieces of wood to make a wider board. Is this feasible with plywood? I have a project made with 3/4" A-1 cherry ply ($$) and am short two shelves. I have some narrower stock from a previous project I could use to glue up the shelves (~ 2 pieces 20" x 20") from ~10" wide stock. I'm not worried about grain matching, and realize the glueup needs to be almost perfect, since I can't sand it flat. Assuming I could do this with cauls, whatever, would it be structurally sound?

[Joe Jensen]

I've done that. I used the jointer to joint each edge. Getting them essentially perfectly aligned is really hard. I made clamping cauls with 5" wide pieces of plywood. I edge jointed them flat too, and then I waxed the edges. When I went to glue the plywood parts together I used biscuits every 3 inches. Today I'd use my domino. You need some way to create more than a flat joint for it to hold IMHO. When I went to glue up, I used a caul on each side, aligned so the glue joint ran right down the center of each caul. I then used Bessey K body clamps to pull the cauls right. A curved caul would be better but I didn't have them. I figured if I didn't have a curved one, I needed a wide one so it wouldn't bend.

My joints came out very well, but the glue squeeze out was some trouble.

[Curt Harms]

This is one of the tasks for which the biscuit joiner was invented. If I didn't have one and wanted to accomplish the same thing, I'd get a slot cutting bit for a router and make my own spline. Some examples. (http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_slot.html)

[Karl Brogger]

You don't need a caul to clamp up a shelf, it will actually make alignment harder. You will want to have something protecting the edges of the plywood from the clamps to prevent mushrooming though. Use a few more clamps and work from one edge to the other, lining things up as you go.

I wouldn't bother with biscuits either. Put the two edges you want to use together dry, make a mental note of the humps and bumps, then glue it up. Also gives you a chance to get your clamps spaced how you'd like. Much more than that is a giant waste of time in my opinion.

[Paul Greathouse]

I've edge glued ply for shelving and cabinet carcass parts when I didn't have time to run to the lumberyard or when I wanted to save buying another sheet just for one piece.

If both sides will show I use biscuits but if only one side shows I use pocketholes on the side that doesnt show. For me, the pocketholes make it easier to line up the edges. I do use clamps to hold the ply in place while I am installing the pockethole screws. By doing it this way I am able to align the edges at each screw location if necessary.

[james bell]

although i have never tried edge gluing plywood, i thought would be to put a (narrow) strip of hardwood between the two pieces of plywood. a thicker strip would allow biscuits.

[Steve Griffin]

Do it all the time, especially with more expensive sheet goods.

Bisquit jointer is the key for alignment and strength. Manually lining it up is a giant waste of time ;) Don't overfill the slots with glue--a drop is all you need. Scrap off excess glue while still gummy and after dry sand with 150-220 ROS and you are good to go.

-Steve

[Eric Gustafson]

I have done it with the Festool Domino.

[Chris Padilla]

Yep: shopmade splines before the biscuit joiner showed...now it is whatever is handy or I feel like using: pocket screws, domino, or biscuit cutter.

[Peter Quinn]

We do this regularly. sometimes with biscuits, sometimes not. Sometimes just as Karl describes, sometimes with a few cauls. Frankly biscuits make me sleep better, as at least half the joint is an end grain butt. You could even use one of those plywood edge banding bits, but treat one half of the glue up like the plywood and the other like what would normally be the solid. Like a double chamfer or tongue and groove, or glue joint type thing. Anyway, for backs of open bookcases that are greater than 4', its a pretty regular event and not that difficult to do.