Your favorite plunge morticing jig

My favorite is a few chunks of MDF/scrap hardwood, clamped tightly and carefully, then screwed together while still clamped. Especially on repeated parts - this gives the exact same results on each piece, every time.

You may have to make a few, but it costs next to nothing, and each mortise is just like the last. (So make sure the first is right!)

When you're d> Been looking around the web (DAGS) looking for a morticing jig to build.

Scroll down to Router Mortising Jigs:

The version I've settled in with is simply a plywood (or lexan) platform with two sliding parallel fences carriage bolted to the bottom of a plunge base. Simple and cheap to make, and a no-brainer to use. I align the tool with the center of the proposed mortise with a pointed "centering bit", then install the actual mortising bit. I start and stop the slide manually at marks on the stock, which are transferred from a story stick to each part.

My tenons are table sawn with a dado blade and crosscut sled, and hand tuned with a shoulder plane, so the manual stop method is good enough for me. I round the corners of the tenon with a rasp or bench chisel. Each part gets one edge aligned to marks from the story stick, and the tenon is tuned to fit properly and lettered to match at glue-up time.

I've also routed mortises on my router table and with a gutter-shaped jig, and like this one the best. Two edge guides will work, as well.

Have fun! Barry

Ok, so here's my dilemma. Do you use a 3/4" or so template collar in the jig you suggested (concerned about chip removal with upspirling 1/2" bit) or do you mount this to your router base. You see there are 2 very different approaches to this fairly simple task (100's of variations of those) and i can't get my head wrapped around one or the other! thanks

Two come to mine:

ShopNotes #90 has a VERY simple one.

Woodsmith 06/03 issue:

Both jigs work well, so it really depends > Been looking around the web (DAGS) looking for a morticing jig to build.

That's exactly what I use. It's an OLD design, I'm sure the first person to ever get a router probably built one the next day.

It won't perform many tasks, but it sure does one very well.

will post pics of mine in abpw.

Joe C.

Take your plywood and tack on parallel pieces of straight stock at the proper interval for your chosen collar. Cut a bunch of spacers for the interval between mortises (less twice the collar offset) and a spacer to set the mortise width (plus twice the collar offset). Tack in the interval pieces, then plunge the plywood to make your template, attach to the fence which you clamp to the stock to be mortised.

Did 52 slats (104 mortises) with one similar on the crib project, and it worked dandy.

If you get it, watch the Router Workshop on PBS a few times. They show basic jig techniques quite often.

Just finished

IME, for chair leg mortises, there is probably nothing more simple, fast and effective than a steady hand and a good edge guide. This seems to be David J. Marks' preferred method.

Are you doing loose tenon joinery?

Some of the jigs with video online:

use transparent plastic rather than opaque plywood for the baseplate, just to give a better view of what you are doing.

David Starr

I made a simple one the opposite of this. Mine is a base that has a solid and movable fence. The solid fence is a support for the router and the movable fence is behind it for the router to slide against. You lay the board to be morticed on top of the plywood against the base fence then another base fence goes next to it and its clamped it together then end stops clamp on top.