Detail of a mortise and tenon joint

How to make mortise and tenon router jigs

How the plunge router tenon jig works

We will see how to make both, a tenon router jig and a mortise router jig. With these jigs we can make tenon and mortise joints easy and fast. Besides once the tenon jig and the mortise jig are adjusted we’ll make the joints with the minimum effort, because we don’t need neither mark the tenons shape in the wooden bar heads to cut them later with hand saw nor mark the mortises shape to carve them later with the chisel.

The first is to decide the width for our tenons and mortises. Our tenon width depends on the short side length of the wooden bar sección. It should be between 1/3 and 1/2 of that length. What we try is to select a router bit which diameter is more or less equal to that measure. If we have to decide between two bits we’ll select the bigger one, because it will reduce some problems routing he tenons (as we’ll see in the video, we can have unrouted corners). I use the same router bit to make the tenons and the mortises, but if we use a bigger router bit to make the tenons it is easier to minimize that problem. If you decide to use different bits just make sure to use the right diameter for each calculation.

How to make the tenon router jig:

How to calculate and draw the tenon jig contour

What we need first is to make a simple box that will help us to hold the wooden bar vertical while we route the tenon in the head. On the top of the box we’ll put a marquetry board with a hole. The edge of that hole will guide our router guide bush to shape the tenon.

We follow the sketch on the left to draw the hole perimeter. We need a square, a set square and a drawing compass. The most important thing is to get a calibre to measure as well as possible the router guide bush and the router bits diameters.

Router tenon jig support plans and cutting diagram

Here you have a cutting diagram with all the box measures and the box outline.

The first video in this post is about making the box. I also explain a couple of problems I had, and how I fixed them. In the second video I explain how to cut the hole, that is the key of the jig.

As I mentioned before, in this second video I show you how to calculate the hole. The explanation is not as good as I would like it to be, so if someone have any doubt I’ll try to solve it.

Finally I just want to say that when we choose a bit we must look for the long ones. The two on the left are from a cheap set and the one in the right is from another cheap set. If we use the short ones it won’t be easy to obtain the tenon length we want.

Tenon in the head of the stripDifferent length straight router bitsThe same tenon in the head of the strip

Now we just have to make the mortises jig, but this one is much more easy to make.

How to make the mortise router jig:

Two mortise router jigs

I don’t have plans to make these mortise router jigs because they are very easy to make. With this jig we’ll route mortises at any distance from the wooden bars head, just adjusting the first wooden bar and repeating the mortise as many time as we want. All we need is make a good base to support the router and a couple of stops adjusted to limit the router movement.

The mortise, with round corners, we can route with this jig

As you can see in the pictures we basically screw two short wooden bars into a piece of plywood and we screw to the wooden bars the stops. Both the distance between the stops and the router bit diameter will determine the mortise length we obtain.

Mortise and tenon jointHow the tenon fits in the mortise in the head of the strip

If we want to change the mortise width we can change the router bit, but that will change the mortise length too, so we need to move one of the stops to adjust the length again. If we just need to change the length we only have to move one of the stops.

In the next video we see how to make and how to use the jig. The only inconvenient is that we need a jig for each different section of the wooden bars we use. Or even two if we want to route a mortise both in the wide and in the narrow face. Anyway these router jigs are easy to make and easy to use.

How to route the mortise so both strips are flush in the edgeMortise and tenon joint flush in the edge of the stripMortise and tenon joint centered in the face of the strip

You can watch in my YouTube channel how I use these router jigs to make a stool.

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