Successfully dovetailing baltic birch plywood. March 20, 2001
I'm dovetailing Baltic birch plywood and experiencing a lot of tearout. I am using a Porter Cable Ominjig 24" with a 1 1/2 horsepower Porter Cable Router. I am using a 1/2" 12 degree dovetail bit, brand new.
Do I need a bit with a smaller angle? Do I need to score the plywood before each cut?
A shallow preliminary cut across the face of the work-piece is usually a good idea when using this type of jig. It quickly scores the surface fibers and prevents tearout when exiting the material each time a pin/tail is cut. Make this cut after getting work pieces aligned and ready to go, then start cutting dovetails.
I dovetail wider stock than I need and rip it to width afterward, because the bit usually blows out the last (unbacked) pin.
When you score, be sure to use a climb cut. Be careful when traveling in the opposite direction with your router.
From the original questioner:
The initial scoring cut barely hits the ply. It actually does not make a cut through the first plywood layer. I am using a 12 degree bit. Should I use a larger degree bit to achieve the depth? I cannot adjust the depth of cut on the jig, because the sides of the drawer (pins) will plunge too deep into the drawer fronts (tails).
Try to use a 1/2" shank bit. Maybe cut a little deeper. Also, remember that the first signs of wear on a dovetail bit will be the points--they're inherently the weak spot. A good way to quickly check a carbide bit for wear is to look at the edge from the cutting side--if it's shiny, it's worn.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor A:
If you are having trouble with the last pin blowing out or tearing badly, do what I do and add a small piece of same thickness material to the side of the one you are cutting the tails into. This adds a backing to the final pin, and all but eliminates its blowout.