Knowledge for the World

How to cut a mortise by hand

It can be tricky to cut a mortise without the help of machines but using this method, I find I end up with mortises as clean or cleaner than what I could get with a drill.

In these interests [?]
1

Mark your mortise very carefully

Many guides cover ways to mark your mortise, so I will not cover that in depth. The standard way is to use a mortise gauge. For this method, you will need to have a chisel the same width as your mortise so keep that in mind when designing your joint.

Mark your mortise very carefully
2

First cut

Begin by placing the chisel about 1/8" of an inch from the right side of the mortise with the bevel facing the left side.

First cut
3

Work your way across an 1/8" at a time

Hit directly down and kind of hard, but don't kill the chisel. You'll see the chisel move away from your bevel just like a good chisel should.

Stop when you get within an 1/8" of the other edge.

Work your way across an 1/8" at a time
4

Place the chisel definitively on the line, bevel facing towards your mortise and hit down

This will be hard and straight down, but still do not kill it. You want to be patient here because over doing it can still create pressure and damage the visible edge of your mortise.

Place the chisel definitively on the line, bevel facing towards your mortise and hit down
5

Work your way back with the chisel at an angle

Chop in with the bevel facing upwards. Do this enough to chop most of the wood.

Work your way back with the chisel at an angle
6

Define the original edge just like we did in step 4

Define the original edge just like we did in step 4
7

Clean out the mortise

Using a much smaller chisel, pry the waste out of the mortise. It is essential that you do not use the wall as leverage. It is extremely tempting but be patient and do not do it.

Clean out the mortise
8

Repeat

If you have a specified depth, check your depth after each cycle. If you're going all the way through, eyeball halfway and then come from the other side.

By the end, you should have a good mortise that requires only slight cleanup with your chisel.