How to Cut a Mortise by Hand (Chisel)?

Learning how to cut a mortise using nothing but simple hand tools is easier than you might think. It’s also a hell of a lot cheaper than using routers or other power tools, and in my own experience, it’s actually highly satisfying.

While it might seem intimidating at first, cutting a mortise by hand is totally doable with just a chisel, mallet, and a few marking tools.

If you’re cutting a mortise by hand for the first time, then I’d suggest practicing on a piece of scrap wood before moving on to the real thing. It will probably take a couple of tries until you get the technique down pat, so it makes sense to sharpen your skill on something that can be tossed away if you screw up.

I’ll break down how to cut a mortise by hand using a chisel, and show the entire process in step-by-step detail.

Tools & Materials

  • Bevel edge chisel(s)
  • Mallet
  • Pencil
  • Carpenter’s square / Speed square / Mortise gauge
  • Clamps or vice

How to Cut a Mortise by Hand – Guide

Cutting a mortise by hand is a skill that will come in handy with all kinds of DIY and woodworking jobs. Everything from installing door hinges to cutting mortises for door reinforcement locks will be a breeze once you get the hang of this technique.

Step 1: Mark the Mortise

The first step to cutting any mortise is marking it out on your workpiece. There are a variety of specialized tools you can use to accomplish this, including a mortise gauge – but these aren’t necessary for marking a basic mortise.

mortise marking
Mortise marked with waste section clearly outlined.

Use whatever measuring and marking tool you have on hand (I used a speed square) to outline the mortise dimensions. Carefully mark the edges with a pencil, and be sure to clearly mark where the waste portion is.

Step 2: Start Chiseling

Start with a sharp bevel-edged chisel that’s the same width as the mortise you want to create. There are specialized mortise chisels available, but they really don’t do a better job than a simple all-purpose bevel-edged chisel does.

I used the Irwin Tools Marples Construction Chisel, and I find it works really well for this job, as it has a flat metal strike cap on the handle that makes powerful and precise cuts possible.

Line up your chisel with the markings you made in the previous step. You’ll want the first cut to be about 1/8” from the mortise edge with the bevel facing away from the edge.

first cut with chisel
Making the first cut with the chisel.

Hit the chisel with your mallet a couple of times and then move the chisel another 1/8” forward and repeat.

It’s important at the beginning to start with shallow cuts and then progress to deeper ones as you move along the mortise. This will prevent chipping and damage to the edges of your mortise and keep the cut even as you progress.

cutting mortise with chisel
Progressing through the mortise. Gradually increase the depth of cut as you go.

Step 3: Cut the Edge

Continue making cuts until you reach the far end of the mortise. When you’re about an 1/8-inch from the edge, stop and flip your chisel around so the bevel is facing towards you.

lining up the chisel with the mortise edge
Lining up the chisel with the mortise edge.

Then carefully line up the chisel edge with the mark you made in the first step. Strike the chisel with the mallet to create the edge of the mortise.

Step 4: Remove the Waste Material

At this point, you’re left with a messy-looking mortise with plenty of chipped wood left attached to it. Rotate your chisel so it’s close to flush with the workpiece and hammer it to remove these loose chips.

You’ll need to repeat this process several times to get a smooth result. If your mortise needs to be a certain depth, then use a tape measure to check the depth as you go.

If you need to deepen the mortise you can do this fairly easily at this point. Simply strike the end of the chisel with your mallet as you did in the previous steps and repeat until you reach the desired depth.

cleaning up mortise with chisel
Cleaning up mortise the mortise.

One thing to watch out for is any knots in the wood. These will make chiseling more difficult and will require more force than normal wood.

Step 5: Clean up the Mortise

When you’ve achieved your desired depth, you’ll want to clean up the mortise. A smaller-sized chisel is useful for this, as it allows you to really get into the tight spots and remove any chips that are still attached.

A useful way to get a nice smooth finish is by scraping the bottom of the mortise using just the chisel and no hammer. This will essentially shave the wood down instead of making deep cuts into it, so you can get a really smooth flat finish using this technique.

shaving mortise bottom
Shaving the mortise bottom.

To do this effectively, you’ll want to make sure your chisel is nice and sharp.

Denis Gardner

I've loved tinkering and fixing things for as long as I can remember. So, naturally, I gravitated towards DIY and home improvement when I bought my first home. Nowadays you can find me writing about my passions or messing around with my newest tool!

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