I've recently cut mortices using a template and busing guide with a plunge router to get easily reproducible results. I then cut mortices by routing away 5mm all round my timber. I then discovered that my timber is not very accurately machined - some tenons were over tight and others too loose.

To fix this in the future I would probably try to fit in a planer/thicknesser, but for my current project this is not practical. I want to have well fitting routed joints but not take away from the woods current finish - which is fine for the garden tubs I want.

How would I go about cutting exact 25x60mm tenons on the end of approx 35x70mm timber? I can't see how a trim router and template would be workable on the end of a small profile like this.


  • General piece of advice, cut the mortises, then do the tenons to fit. It's much easier to adjust a tenon from over-tight to a tight sliding fit than trying to remove the tiny amounts of wood necessary from the sidewalls of a mortise! And if necessary to adjust for a sloppy fit, it's far easier to glue shims to a tenon than to glue them inside a mortise. – Graphus May 13 '18 at 16:04

I'd look to the typical hand-tool workflow for cutting tenons and adapt it to the router. Working with hand tools it's generally assumed that one face will be your reference for all your layout. That way if the piece is slightly off in thickness or slightly out of square you'll still get a good joint.

So I'd start by laying out all of your tenons with a double marking gauge. This is a tool that has a fence and two adjustable cutters. The cutters are set so the distance between them is the same as the width of the mortise and the distance from the fence to the near blade is the width of the mortise's shoulder.

Once you've laid out all of your tenons you can cut all of the reference-face cheeks with one router setup. For the back face you'll have to adjust the bit depth to hit each layout line before you route the cheek.

  • 1
    This will depend of course on the two faces being parallel (enough). Otherwise you'd need some sort of adjustable platform to support the router base in a plane parallel to the first face. I would definitely choose the thickness planer route in that case :) – scanny May 12 '18 at 7:13
  • 1
    Thanks' for the answers. I used the double marking gauge and adjusted the cuts for the back sides. I'll definitely be looking for a planer / thicknesser to simplify the process in the future. – SteveGroom May 13 '18 at 6:23

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