How to cut a mortise with a chisel?

 One of the oldest and strongest known carpentry joints is the mortise and tenon joint. And in this blog we want to share with you about 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. 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.

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.

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.

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.

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.

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.

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.

• 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.
• 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.