Thread: Yet another mortise jig!

I thought I would add my mortising jig to the list. It may not be for everyone, but it is every easy to set up, foolproof in use, and provides very safe overhead mortising for both long and short lengths of timber.

The jig is built into a portable bench vice (mine is an old German-made double vice bench that I have modified. A Stanley Benchmate or similar could be substituted) and basically consists of a clamp for the timber, a flat surface on which the router will run, plus a guide for the router.

The router used is my Elu 177e, and the guide is one adapted from a Hitachi (I think) that I picked up in a flea market for $5. It was chosen as it has a fine adjustment mechanism (used here for lateral movement). The modifications are evident in the picture. The important feature is that the router guide fence runs in a slot (it connects from below), and this prevents any tipping. Screwing on a hardwood runner plus two spacers creates the “slot”. Cut the spacers and the router fence from the same piece to guarantee a nice tight fit. Wax it for easy movement.

It is not evident in the pictures, but stop blocks are used to limit the travel of the router so that repeatable cuts can be made. I also use a “registration mark” to help line up the router bit and the one end of the mortise.

Choose the router bit you need. Slide in your timber, line up one end of the desired mortise with the registration mark, clamp down, position the router in- or outwards with the fine adjustment screw, and plunge cut your mortise. This is now repeatable.

While I also chop mortises by hand, this jig was a lifesaver for the 84 mortises that had to cut when I built a king size Mission-style bed in Jarrah last year. From memory they took about 1½ hours from beginning to end.

Picture #1 is a general view, #2 is a close up along with clamped timber, and #3 and #4 are close ups of the guide.

Regards from Perth

Derek