How To Cut a Mortise With a Chisel

Cutting out a mortise is one of the basics of joinery when it comes to woodworking. When you think of cutting a mortise, you usually think of using a router or Forstner bits. But the best way to cut a mortise is by hand using a chisel. This method of cutting out a mortise is much cleaner, more effective, and faster than any other. You can cut out a mortise within minutes using a chisel. Not to mention you have complete control of the depth and width with it. If you don’t know how to do it yet, don’t worry, we have you covered with this guide on how to cut a mortise with a chisel.

To cut a mortise with a chisel you first need to mark its width with a mortise gauge. Once you do that, place your chisel perpendicular to the marked area. Make sure the bevelled edge is facing away from the edge of the line that you marked for the mortise by 1/8-inches. Using your mallet, strike the chisel and it will start to dig in. First, make a pass all the way to the other end of the marked line. Then turn the chisel around and then make another pass to the other end. Once done, you will have a clean mortise that you can insert a tenon in.

Unless you have to cut a few dozen mortises in a short amount of time, a chisel is a way to go. For mass production though, a machine might make short work of the wood than you could with hands. Besides, it is a great skill to have in handy in case your machines aren’t working. Not to mention it gives great satisfaction to carve a mortise with a chisel, it will give you such clean cuts. Also, if you want to start working on handmade joinery, it will give you a head start on how to control and carve out wood with a chisel.

Step by Step Guide on How to Cut a Mortise with a Chisel

To cut a mortise, you need to use a solid and sharp mortise chisel in your arsenal of woodworking tools. A flathead or a bench chisel is too thin to be used to carve out a mortise in wood. When using a mallet to hit it from behind these two might get a damaged edge. But a thick solid mortise chisel is designed for this heavy-duty job.

Step 1 – Preparation

Before anything, you need to prepare the tools that are required for carving out a mortise. A mortise chisel is pretty basic and everyone will have that at hand when carving one out. But you also need a clamp to hold your piece of wood securely while you carve a mortise. A bench vice won’t do for hardwood as it might slip out while you are carving it out. You also need a mortise gauge and a square for marking out the mortise on the piece of wood. Lastly, you will need a mallet for the chisel, if you have a steel-capped chisel then a rubber mallet will be needed instead of a wooden one.

Note: Make sure your chisel is sharpened properly before you use it for precision and efficiency.

Step 2 – Taking Measurements

Using your mortise gauge mark your piece of wood where you will be cutting out a mortise with your chisel. Once you are done with that, use a square to mark where you will be placing your mortise to start cutting. But you will not place your chisel exactly at the mark when making the first pass. That is because the bevel always ends up pushing the chisel away. So you want that small leverage that will allow you to not exceed the marked measurements.

Step 3 – Making the First Pass

Place your mortise chisel perpendicular to the surface of the wood 1/8 of an inch away from the marked area. Place the bevelled side away from the edge and start cutting by firmly striking the cap of the chisel with a mallet. It will dig in deep while slightly moving towards the edge due to being pushed away by the bevel. This is the reason why you place the chisel 1/8 or 1/4 of an inch away from the edge of the mark. After the first strike, keep moving 1/4 of an inch away and keep striking with the mallet. You will notice each time you strike the chisel it digs deeper. Go from one end all the way to the other and make the first pass.

Note: Mark the chisel with tape to make sure you don’t cut too deep into the piece of wood while carving out a mortise.

Step 4 – Making the Second Pass

As you get finished with the first pass you will have dug quite deep into the wood. But it will look like a curve inside the mortise at the moment, you need to make it straight and clean inside for the tenon. So turn the bevel around making it face the other way from where you started and place the edge of the chisel right on the mark. You are placing this on the mark because there isn’t enough wood there to push the chisel away from the area of impact towards the mark. Now start making the second pass towards the edge where you started off. This will take out the curve and make it straight inside the mortise.

Step 5 – Cleaning Up the Mortise

Once you almost reach the edge where you started cutting the mortise, you can pry the chisel inside to lift up all the material that was carved off and clean it up.

With the clean-up done, you will now end up with a straight and clean mortise ready to accept the tenon that you cut out. Here is a detailed video where it can be seen why cutting a mortise with a chisel by hand is more efficient:

The Best Chisel for Cutting Mortise

One of the best manufacturers of chisels is the Narex brand, which is why this Narex Mortise Chisel is our recommendation. It is 14mm in size with a beechwood handle that can withstand plenty of abuse from a mallet.

Best Uses for Homemade Mortise

A mortise can be used for many things, in construction, it is used for panelling and framing walls. It works better than just nailing some boards together, as a mortise holds stronger and lasts longer. For a homemade mortise, you can make a chair out of it, cabinet, frames, doors, and even windows. The possibilities are endless as long as you keep an open mind about them.

Tips for a Perfect Mortise

  • Always sharpen your mortise chisel before starting any cutting projects. The sharpened edge will make sure there aren’t any errors and your chisel isn’t struggling to carve into the wood.
  • Stick a piece of tape on the mortise chisel to know how deep you are cutting. It will act as a gauge to help you stop at a certain depth.
  • If you don’t have a mortise gauge you can do just as well using just a square as well.
  • Strike the chisel only once firmly with a mallet as you move from one mark to the other.
  • Use a pencil to mark where to start cutting to make sure you don’t make any errors.
  • Be patient, let the chisel’s edge do the work for you, don’t use excessive force on the mallet and strike it uniformly throughout.
  • Clean the mortise when you are cutting it by prying out the shavings and chips using the chisel itself.

Alternative Ways of Cutting a Mortise

We already touched up the alternate ways to cut a mortise earlier. Usually, people use a router to cut a mortise, it is pretty easy once you set up the jig. But it takes more time to set up the jig and the router than it does to cut a mortise by hand. So unless you plan on cutting a dozen mortises, we recommend doing so by hand as it will be faster than setting up and cleaning up afterward. All you need is a chisel, a clamp, a square or gauge, and you are done.

The second way to cut a mortise is to use forstner bits to drill into the wood and then use a paring chisel for squaring it up afterward. This method is mostly preferred by woodworkers who don’t want to use a mortise chisel to cut out a mortise. Most people have a drill press at the ready in their workshops, and they just need to change the Forstner bit and drill. So it takes slightly less time than setting up a router and a jig for cutting mortise.

Though squaring up after using a paring or bench chisel takes as much time as the first method. This is why some woodworkers just use a mortise chisel instead. Not to mention woodworkers often find it satisfying to do it by hand using a chisel.

Final Thoughts

Although an incredibly easy task, some people avoid cutting a mortise using a chisel because they feel it might be inaccurate. But if you follow the step by step guide we have given you, it will be more accurate than what you do with any machine. Also, practice will bring you closer to perfection when it comes to cutting a mortise by hand using a chisel. So keep practising and you will start to enjoy cutting out mortise by hand more than using any machine to do the job.

Martin Swizz

Hi! This is Martin, I like to research, experiment, and learn new things related to wood carving and other kinds of woodworking.

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