Box joints would seem to be ideal for joining plywood, but even with a brand new dado set I am unable to keep the backs of fingers from chipping badly. What should be a handsome joint ends up a mess. Do I have bad plywood, or am I doing something wrong?
Steve22
Replies
Steve,
You need to put a "backer" behind the piece you're dadoing. If the cut in the backer becomes enlarged, make and use a new one.
Gary W
gwwoodworking.com
Thanks for the reply. How is a backer different from the body of the jig which has a fresh cut made by the dado? I'm using the technique shown in the Fine Woodworking video "Tablesaw Box-Joint Jig - Produce tight-fitting joinery for boxes and small carcases in a few steps with a simple fixture for your tablesaw with Gary Rogowski". Gary recommends a cutting gage scoring to reduce tear-out, but I'm getting chipping on both the sides and above the cuts.
Edited 1/21/2008 10:33 pm ET by Steve22
Well, I've made at least a thousand or two finger jointed plywood drawer boxes, and I always used a throwaway backer to prevent tearout. I used a special sled and gang cut up to ten, 1/2-in-thick, 9-ply sides or backs at a time. By clamping the stack against the backer, which was between the stack and against the sled's fence, I never had tearout. I suppose you could score each individual cut, but I can't imagine how much time that'd take. The backer was of scrap, usually a piece of the same material as the drawer boxes.
I don't make drawer boxes any more. For the past six or seven years, I've employed a shop that specializes in dovetailed drawer boxes that I purchase pre-finished. Economically, they're about half the cost of the boxes I made in house. When I bought a sliding tablesaw, I gave away the drawer box sled to a guy that still uses it, I'm glad to say, and he produces some pretty good products.Gary W
gwwoodworking.com
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