Baltic Birch Plywood Dovetail Tearout Problems

Dry veneers on plywood are brittle and tear out easily. These tips may improve your results, though. February 20, 2008

Question
I recently started making drawer parts from Baltic birch plywood, and am having a hard time preventing a little tearout at the dovetails. I was making parts from solid wood, but the cost is becoming prohibitive. I use a Porter Cable jig and router. Any ideas?
Forum Responses
(Cabinetmaking Forum)
From contributor P:
Higher bit speed, sharper bits, and backing the piece. I don't have the Porter Cable jig, although I told Santa I want one, but doesn't it require a backer board for through dovetails? I use hardboard templates when I make router cut dovetails and back the piece with hardboard or 1/4" ply and don't have much tear-out.

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From contributor B:
I use the PC jig and PC router. You can make a light pass in each direction as you enter the slots and that helps. I kind of move the router back and forth before pushing it back into a slot. Also make sure you have an extra piece on the top of the jig to ensure there is something behind all portions of the vertical piece. That said, you will still get some tearout, even on high speed with a new bit. Be careful and you can minimize it. Use some wood filler to repair any damage if you can't lay the original wood back in there with some glue. An alternative might be to add a piece of scrap in front of the vertical piece. Hardboard would work and it is cheap.

None of my customers were asking for dovetails, so I just quit doing them and now use butt joints with glue and staples. They are very strong and I don't waste time cutting dovetails and repairing tearout.

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From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
The basic problem is that the veneer was over-dried before it was manufactured into a panel. It will be brittle indeed. This cannot be repaired. Using HSS rather than carbide will help, as will shallow or small cuts, as suggested above.

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From contributor M:
If you don't need the wages from making the dovetail drawers, you might consider ordering the drawers from a component specialist. I recently tried this for the first time, and I got Baltic birch dovetailed drawers, pre-finished, and they only cost me about $25 per drawer. I was very pleasantly surprised.

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The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor S:
I was going crazy trying to get clean dovetails in my prefinished baltic birch plywood. After watching Norm use his jig to cut dovetailed drawers in the same material, I knew there must be a way. There must be a sacrificial backer board on both the front and back sides of the work pieces. Using my Porter-Cable 4212 jig, I found a way to easily clamp a backer board to the front side of the vertical piece. I was able to simply attach a horizontal piece of wood between the two large adjusting knobs in the front. I cut notches in both ends so the piece simply rests on the top of the knobs. Then using t-nuts, I put bolts and knobs to clamp the backerboard to the work piece. After using this method, I now have very clean cuts.