Q:

When routing mortises like in “A Guide to Guide Bushings” (FWW #207), I use a bit that’s the same size as the mortise, but my mortises always get packed with wood chips, which really slows down the process. How can I avoid this?

Ross McPherson, Coleman, TX

A:

Excavating the waste when you’re routing a mortise improves the quality of cut and keeps wood chips from getting caught in the mortise. Here’s how I keep my mortises clean.

Start with a router that can be connected to a shop vacuum. This way you can remove the chips from the mortise as they are created. You should also use an upcutting spiral bit, which pulls the chips up and out of the mortise.

It is also essential to choose a guide bushing that allows plenty of clearance for wood chips to flow past easily. In my experience, 1/8 in. of clearance is plenty. That means, when cutting a 1/4-in. mortise, use a 5/8-in.-dia. guide bushing.

Technique matters, too. Cut the mortise using multiple shallow passes, increasing the depth a little with each cut. As a general rule, the depth of each cut should not exceed the diameter of the bit that you’re using. This will reduce the volume of chips created at one time, so they don’t get packed in the mortise.

Photos: Staff; Drawings: Kelly J. Dunton

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