What Is A Mortise And Tenon

Introduction

It doesn’t matter if you are a highly experienced woodworker or just starting out , the mortise and tenon joint can be used on almost all projects. It’s regarded as one of the strongest and best ways to join two pieces of wood at 90 degrees.

What is a mortise and tenon joint

A mortise and tenon is made up of two pieces of wood that are joined together by inserting one end of the piece in a hole in the other piece. It’s that simple. The piece of wood with the smaller end is referred to as the tenon and the corresponding hole is the mortise.

How to layout the tenon

First of all you have to establish how deep you want the tenon to go. This is dictated by the thickness of material and whether or not you want a thorough tenon or not. Once you have established the depth, you can mark out what is called the shoulder using a marking gauge. 

How to layout the mortise

To get the best result you have to layout the mortise and tenon at the same time using the same setting on the marking gauge. So when you have decided the height of the tenon, proceed the layout on both the piece with the tenon and the piece with the mortise. Use the same method when establishing the width. 

Remove the material

Tenon

Now that you have all the lines you need it’s time to start cutting some wood. The most crucial part to get right is the shoulder on the tenon side. This is what you are going to see when the piece is finished and you want a crisp 90 degree edge for the best result. There are many different ways to cut a mortise and tenon but I have found that the fastest and most consistent way is to cut the shoulder on a sliding table saw. 

The other thing to keep in mind is to first cut the tenon a little bit oversized and then come back to finnes the fit with a chisel or hand plane to get that snug fit we always strive for.

Mortise

This is a little bit more tricky and time consuming. But one way is to remove the bulk of the material using some sort of drill bit. Just keep everything inside the lines and come back to square up the holes using a sharp chisel.

Finnes the fit

No matter how careful you are, wood is an unpredictable beast and you still might need to make some adjustments, usually to the shoulder. This can be done with a shoulder plane or a chisel. 

Different variations

Open mortise

This is basically a glorified half lap joint designed like a mortise and tenon that is open on three sides.

Stub mortise

Here the length of the tenon is decided by the thickness of the material. It can’t be longer than the material is thick.

Through mortise

Here the mortise is cut all the way through leaving the tenon visible on the other side. The tenon can be cut flush with the material or protrude as much as you want it to.

Wedge Half Dovetail

This is a variation of a stub mortise. But you cut two slots in the tenon to receive a wedge. So when you put the joint together, the wedges force the tenon to flare out making it near impossible to take apart again. 

Through wedged half dovetail

Same concept as the last one but with a through tenon. This is a very decorative and strong way of making this joint. 

Loose tenon

As the name states, the tenon is loose and you cut two mortises and everything is held together with glue. This is usually cut with a router or even easier, the festool domino.

Pinned tenon

Reinforce any mortise and tenon by drilling a hole through and putting a pin in it!

Tusk tenon

Another way of mechanically holding a through mortise is with a wedge that you punch through on the outside. Preferably used if you need to take the piece apart again. 

Conclusion

There are obviously a lot of different ways to cut all of these joints. All the way from using your teeth to a full blown CNC operation. My best advice is to use the method that your budget allows. You can get perfect, more rewarding results with hand tools.

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