creating groove in plywood face with router bit

[Don Morris]

I was starting to use a tongue and groove cabinemaking set to unite some plywood to an anticipated maple face frame. I guess I just wasn't thinking. I just happened to have the plywood base cut first and decided to put a groove on the top at the sides of the base so that the plywood sides would be anchored securely and additionally help me align them (plus a couple pocket screws). When I ran the top sides of the plywood base across the groove cutting router bit of course I had a tremendous amount of tearout along the entire length of the groove. Will that only work on the ends? Is there any way to cut a dado like groove on the face of plywood without the tearout? Tape it? Is taping OK to do with a router bit? Or is a redesign in order?

[Mike Marcade]

If I understand, you are trying to dado the face of a sheet of plywood. I have done this but I think the results will really depends on the quality of the plywood you are using and how sharp your router bit is.

The tape may help. Give it a try.

[Ken Deckelman]

Tape will help some, but scoring the ply with a sharp utility knife is the real answer.

[Don Morris]

I'm using furniture quality maple plywood so that's not the problem. I'm going to try a small sample with tape on it. I've been hesitant to try that because I don't want to mess up my new cabinet making router bit. A very small sample shouldn't hurt. Will score it too!!!

Thanks guys!

[Rick Moyer]

I recently routed two dadoes (1/2 in) in oak faced ply and had no tearout, so I would guess the bit may not be sharp?

[Steve Jenkins]

A sharp bit is a must and a downcut spiral bit wil make all the difference in the world.

[Doug Shepard]

A downcut spiral would probably work best but even a regular straight bit can work well if you do a scoring cut first - just barely into the top veneer layer, then deeper for the actual groove.