# Plywood splitting



## LinkC (Aug 17, 2008)

I'm dovetailing some of that 1/2" pre-finished plywood drawer stock and I'm having trouble with the router splitting the first ply off, particularly in the area of the pre-made groove for the drawer bottom is. It really messes up the inside of the drawer side.

Any suggestions?

I'm wondering if some sort of thin backer board might help. How would that affect the jig settings?

Using Rockler "old" half-blind jig w/ 1/2" template, if that matters...


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## bobj3 (Jan 17, 2006)

Hi LinkC

Plywood can be nasty to put in dovetails, a backer board will help out of 1/8" or 1/4" thick MDF....

You may want to put in box joints or a drawer lock joint in place of dovetails...


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LinkC said:


> I'm dovetailing some of that 1/2" pre-finished plywood drawer stock and I'm having trouble with the router splitting the first ply off, particularly in the area of the pre-made groove for the drawer bottom is. It really messes up the inside of the drawer side.
> 
> Any suggestions?
> 
> ...


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## Check twice! (Feb 11, 2008)

Good day LinkC and a warm welcome to the forums.

I have done box joints with a table saw for the reasons you give, trying to do dove tails in plywood. I have tried several methods and have failed with dovetails and plywood. Others may have had luck but not me.

I use a box joint method of joining ply since then and my tablesaw. As Bj suggested you may want to give this a try. 

A couple of photos of 1/2" ply and box joints, they are clean and I have had very little issues.

John


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## karateed (Feb 7, 2006)

So that's what BJ means.....Box Joint.

Ed......


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## Microsuffer (Aug 7, 2008)

LinkC - 

Would you mind adding some pictures? I'm interested in seeing the wood still in the jig with the tear out showing, if possible. It might also help others suggest a better fix, and, if not entirely familiar with the jig, possibly answer your question about the effect of the backer sheets on the jig settings.

The Rockler is supposed to accept up to 3/4 stock so you should be able to mount a 1/4 sacrificial piece against the slot side of the 1/2 inch plywood. I think 1/8 masonite is marginal, but worth a try on some scrap.

Tearout with dovetails happens in any material if the exit side of the cut isn't adequately supported, either because the neck is too skinny for the material or your cut is too close to an edge. Backer boards help with this, but aren't always possible or fully effective. 

Another, probably obvious idea is to see if you can shim the material to reposition the cuts such that the slot exits through a cut. I've done that to deal with just this kind of problem.

When putting dovetails in plywood I normally sandwich the work between sheets of poplar (small dovetails) or MDF (larger). The concern here is to have strong enough backer material so the bit doesn't blow away the backer just before blowing out the work. Very annoying when that happens. Of course, I use an Incra-Jig where I can stack up both drawer sides inside backer pieces without any concern about thickness.


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