Furnishing a Sauna Suite #9: Routing Leg Mortises

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Blog entry by DustyMark posted 01-26-2021 02:38 AM 405 reads 0 times favorited 0 comments Add to Favorites Watch
« Part 8: Processing Rough Lumber Part 9 of Furnishing a Sauna Suite series Part 10: Suction-Fit Tenons »

Router Jig or Mortise Machine?

With all the wood cut to basic dimensions, it was time to begin joinery. I’m making the mortises in the legs for the two benches and the table in a batch. Would I use the mortise machine or my ancient/effective plunge router jig? I did a test cut in one leg and discovered that my 5/16” spiral upcut bit was up to the task. It didn’t burn the ash (I usually use cherry which burns pretty easily.) and I was able to plunge 3/4” deep mortises in four passes…router jig it was.

Simple Jig

I saw this jig in an old Fine Woodworking book and have used it for over 30 years to cut most of the mortises in a house full of furniture. It’s a simple U-channel box made of plywood with fence stops secured by European knock down fasteners. Shallow wedges hold the work in place. I use spacer boards underneath to raise the work to the proper height. The extra plywood under the jig was from when I used it on my lathe to route grooves on turned chair legs to receive laminated braces. (I really should build a longer jig to work with the longer fence of my new plunge router, but you know how that goes!)

I had marked the mortise limits on the legs since I was pretty certain I’d use the mortising machine.

Once the fence stops are set, only the longitudinal center of the leg mortise needs to be marked and centered on the line scribed in the face of the jig. I scribble the outside edge of the leg where each mortise will be routed. This helps me to avoid routing the mortise on the wrong edge!

The wedges only overlapped slightly on the legs. On 4/4 stock, the wedges contact each other and provide powerful clamping force.

The mortises are much cleaner than the mortise machine produces. I won’t even have to chase these with a chisel.

After experimenting with the first leg, the remaining 22 mortises only took 36 minutes to route at a comfortable pace. That’s not bad for a non-production, home-shop jig!


Cut tenons for the rails.

-- Mark, Minnesota

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