Chipout on plywood creating dovetail

[Jeremy Thompson]

I'm having a problem doing some dovetails on 3/4" Birch plywood. I have a brand new PC 4012 jig w/ bit and I'm using a DeWalt 618 Router. I'm getting some really bad chipout and just tearing up of the plywood. I start the bit going into the wood very slowly and it's either tearing up the board right as it goes in, or it'll start just shreading it while it's in mid-cut!

The bit is brand new and came with the jig. It looks clean and I can't see any problems with it. I tried cutting some solid poplar I had laying around and it seemed to cut just fine. But, when I try the plywood, it just tears the layers apart! I mean it will actually kick back a few of the layers at you when It gets half way in.

So, what am I missing here? Is it a technique thing or is there a chance the bit is bad and I just can't really tell? Suggestions? :D

[John Lucas]

Jeremy,
It aint easy particularly with the plywood we buy these days. But here is an article I wrote on the subject.
http://www.woodshopdemos.com/sstat-206.jpg

http://www.woodshopdemos.com/sstat-21.htm

[glenn bradley]

I'm sure John will cover climb-cutting but ply is very difficult.

[Jim Becker]

I'm sure John will cover climb-cutting but ply is very difficult.

Exactly what I was going to say...that initial climb cut across the face is critical even in solid stock, but with plywood, even with the "good stuff", there is still great risk of the material chunking out or otherwise having an imperfect joint. This is the primarily reason I don't use ply for drawer boxes other than the fact that I don't like the look of the plies.

A solution, however is to use through dovetails and rotate the drawer box so that the visible joinery is hidden by a false front. There should be no tearout evident in that case.

[Jeremy Thompson]

Guys, thank you for the replies and information. Well, I guess I'm glad it's not just me or the tools! The downside is I have 4 sheets of birch ply that it sounds like it's going to be a real pain to work with. The joys of woodworking :)

The reason I used the ply, instead of something like solid maple, was because I'm creating the NYW workshop hutch and in the video he say he uses 1/2" ply for the drawers (I was testing on the 3/4" birch that I had left over from the box). Being new to woodworking, I didn't realize this could be a challenge!

John - Thanks for the link. It's an excellent guide that i'll have to try to use!

[Thomas Pender]

Jeremy-

I have the same problem with my Liegh jig. So, I gave up on using plywood on the front and back of drawers (pins). Instead, I use 1/2" poplar and it works fine - even perfectly. NFP sells it where I live and there may be others who sell it - they call it drawer stock. I do use 1/4" scrap plywood to back up the tails for the sides as the bit routs through the back and it helps a lot. More than 1/4" and it does not fit in the jig with 3/4" birch. I suppose 1/8" might work as well.

I have used variations of John's methods as well, but the quality of plywood is iffy and when I am making drawers for high end furniture, I do not use plywood because I have to edge band the top and because wood that meaches the drawer face is cool. Alternatively, I stain the front on a half-blind application and then use unstained QS ash or poplar (for contrast). I also tend to rout the top of the drawer side with a fingernail bit to give it that nice shape.

[Charles Lent]

It's usually easier to use one of the drawer joint router bits when using plywood for your drawer sides instead of trying to cut dovetails in them. They make very strong joints with much less chip-out. About the only way that you can make dovetail joints in plywood without getting chip-out is to clamp a sacrificial backer board on both sides of the plywood and then cut the dovetail through them, and this is frequently not possible with many of the dovetail jigs that are available.

Charley

[Loren Hedahl]

I had the same problem. I tried laying out the dovetails on the wood and scribing the veneer ply with a sharp knife. This seemed to almost eliminate the tear out, but took quite a bit of time.

Now I avoid ply for dovetails unless I want to cut them with a band saw and jig saw.

[Jeremy Thompson]

All great suggestions and comments. I'm just going to try what I can see what happens. It sounds like scoring the wood and trying to sandwich it is my best bet.

I also wondered if using blue painters tape would help the chipout at all. Maybe go from one side to the other and then wrap a piece all the way around. I may try that on some scrap, just to see what happens!