How to Perfectly Make A Traditional Mortise and Tenon Joint

Ian Mutuli
Updated on
Ian Mutuli

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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If you’re a woodworking enthusiast or DYI hobbyist, you by now know that the mortise and tenon is an essential joint in woodworking. Besides, the mortise and tenon joint is usually not just one joint but a whole family of joints. There are different mortise and tenon joints, with each designed to fit a specific structural or aesthetic need. Also, you can cut the mortise & tenon joints with power tools, hand tools, or some combinations of the two.

What is a Mortise and Tenon Joint?

A mortise and tenon joint usually joins two pieces of wood or other materials. Most woodworkers have used it worldwide for a long time to join pieces of wood when the adjoining pieces connect at right angles. The mortise and tenon joints are sturdy and stable joints that you can use in many projects. Besides, this joint is usually considered one of the strongest joints after the common dovetail joint.

The mortise and tenon joinery furnishes a strong outcome and joins by gluing or locking into place. It also gives an appealing lookout. So, when shaped properly, you can use it as decorative elements in the finished appearance of furniture.

However, the main downside to this joint is the complexity in making it because of the clear-cut and tight cutting required. But before we can discuss on steps involved in cutting the joints, let’s look at some of the hand tools you will need for cutting mortise and tenon joinery.

What are the Hand Tools for Cutting Mortise and Tenon Joints?

Mortise and Tenon Joint


Here are some to use when cutting mortise and tenon joints:

  • Marking knife
  • Carcass backsaw
  • Joiner’s Mallet
  • Dovetail saw
  • Brass wheel marking gauge
  • Wood chisels
  • Woodworking clamps
  • Fine tip pencil
  • Pig sticker mortise chisel

If you’re a beginner, we recommend you buy a cheap pre-dimensioned wood like poplar for practicing:

  1. Ensure it is square, straight, and flat.
  2. Make some mortise and tenon joints, one after another, to master this method.
  3. It would be best to have a dual marking gauge or mortise gauge to speed up the cutting process.

What are the Steps of Cutting a Mortise and Tenon Joints?

Step 1: Layout the Boards and mark the tenon’s shoulder line

Mortise and Tenon Joint


This initial step involves laying your mortise and tenon boards out on your worktable and bump the tenon board up against the mortise board to see exactly where you want the two to join. Make several marks and make reference marks with the marking gauges to help you remember which faces your reference faces.

Next, mark the shoulder line. The tenon’s shoulder line is where the tenon will come to a close against the mortise. For instance, when putting your head in a tiny hole in the ground, your head will go in; however, your shoulders will stop at the hole’s top. So, lay the tenon on top of the mortise and choose how deep you want it into the mortise.

If you are making a common hidden tenon, draft your board, so it stops at the end of the back of the mortise, around 1/4 of the way back, then make a tick with your fine tip pencil on the tenon board. Conversely, if you are making a “through-tenon”(a tenon that goes through the mortise), then draft your board so that the tenon extends to the other side a little and make a tick mark:

Lastly, set a marking gauge on your tick marks and scribe the ” should line” all-around the tenon. Then, you can set the marking gauge on the tenon’s end.

Step 2: Mark the mortise and tenon joinery

 Mortise and Tenon Joint


The second step is to mark the mortise and tenon boards with a marking gauge (dual marking gauge) or a mortise gauge. Since every board has a different thickness, always do all the markings from the same reference face to make sure the tenon will match with the mortise.

First, place your mortise chisel on the tenon board’s top edge (centering it by your eyes) and adjust your marking gauge’s inner cutter to get in contact with your mortise chisel’s edge. After adjusting the marking gauge, scribe around the tenon’s end from shoulder line to the next shoulder line:

Without changing the marking gauge measurement, transfer the line over to your mortise boards’ inner edge and scribe it where your tenon will go into the mortise hole. Then go on and place the outer cutter to line up with the mortise chisel’s outer edge.

Then, like before, scribe the tenon’s outer line, all around the tenon’s top from shoulder line to shoulder line: Maintain the same measurements on your marking gauge and scribe the mortise board’s outer line. However, if you are making a “through-mortise,” ensure you mark both mortise’s edges.

Furthermore, if you’ve multiple mortise and tenon joints to build, then you now realize how much time a dual marking gauge will save you. This discovery is because you will not have to keep re-creating the measurements over and over again. Instead, you will keep both measurements always locked into your gauge.

 Step 3: Cut the faces of the tenon

Mortise and Tenon Joint


On this step, use a backsaw to cut the tenon’s faces ( “cheeks”). It would be best to use a backsaw with rip teeth since you will be cutting down the grain. However, if you are cutting a small tenon, then a small dovetail saw will work perfectly. But if it’s a larger tenon, then a rip teeth tenon saw is the best option.

Use a bench chisel to chop off a little trench to offer your saw with a tract to start into the cut. This trench will help with stability and straight cutting. Next, start cutting horizontally across the top end grain at about a 45-degree angle, staying an inch to the waste side of the line, and once you have made a shallow kerf on the board’s top, move back about an angle of 45 degrees and keep cutting down to the shoulder line.

Then flip the tenon piece around in the vice and start cutting from the other side; however, in your new kerf created on the board’s top. Besides, the kerf will guide your saw downward in a precise fashion. You can now saw horizontally but ensure you stop before getting to the shoulder line. Repeat the same tenon’s marking process; then, you will have two saw cuts running down the tenon.

 Step 4: Cut the shoulders and tenon cheeks

Mortise and Tenon Joint


After cutting the faces, shift to cutting the tenon cheeks and shoulders. So, since some of these cuts will be across the grain, it would be best to use a different backsaw with crosscut teeth, e.g., a carcass backsaw. However, if you can’t afford a backsaw yet, you can still use the rip dovetail saw, but the cutting will be a bit harder, and you won’t have a clean cut. Instead, you will have to clean it up with a tenon chisel.

After that, secure the tenon piece against a bench hook and deepen your shoulder line with a wooden mallet and a wide bench chisel. Set the chisel accurately in your shoulder line (that you created, remember?). Besides, one or two strokes with the wooden mallet are deep enough. So, ensure your chisel’s bevel is facing the tenon.

Then, use your wide bench chisel to create a small angled trench that will guide your carcass saw. This trench will let your backsaw lie against the shoulder and offer a more precise guide when cutting downward. Then, place your crosscut carcass saw in the trench and cut it straight down. However, be careful not to saw too far. Slowly and steadily, “creep” up to the shoulder line and repeat on the other side.

You don’t have to be embarrassed if your sawing wasn’t perfect since you can straighten up your tenon “shoulder” and cheeks” with your bench chisel.

Step 5: Chop the tenon sides off

Mortise and Tenon Joint


Using your square to draw vertical lines on your tenon on both sides. Scribe vertical lines and cut off a tad from every side with your dovetail saw, then use a crosscut carcass backsaw to chop off the side shoulder. These measurements are not important in this step since you will scribe the mortise width regardless of the size you trimmed your tenon to; therefore, it will fit tight.

Step 6: Mark the mortise

Mortise and Tenon Joint


Place your finished tenon on your mortise and make a tick mark at your tenon’s edges using a marking knife. Then, using a marking knife and combination square, scribe a line from the tick marks so that you have the full layout. You will realize that the crossed-out section is where you need to chop the mortise out with a mortising chisel.

Step 7: Chop the mortise. 

Mortise and Tenon Joint


The time to use your mortise chisel for chopping the mortise is now. First, hold the mortise board stable between the clamp and a board and place it on another board. Since we have the lines to follow while chopping the mortise, ensure your mortise lines’ width perfectly matches the width of your chisel. And the sides of the mortise chisel barely touch your layout lines.

Note: You don’t want the chisel to chop on the end lines initially; otherwise, the force and expansion will deepen your mortise opening, which would end up preventing a perfect fit of your tenon joint. Therefore, start shopping with your mortise chisel, virtually 1/4-inch away from every end of your mortise lines. You will need to use a wooden mallet to hit the mortise chisel’s top when chopping it. Besides, the angle of the bevel of your mortise chisel will cause the mortise chisel to go downward at a particular angle.

Keep chopping until you experience some resistance, pull out the chisel from the rectangular hole, “walk ” it down the board’s edge a bit, and then chop downward again. Repeat this process until you get within 1/4 inches of the other end of your mortise, then stop. Then, flip the mortise chisel around and repeat the whole chopping process once again, going the other way, trying to start the level of your chisel on an unchopped spot.

However, don’t wiggle the chisel sideways when pulling it out of the mortise hole because it’ll alter the width of the mortise hole. Also, try not to use your chisel to pry loose chunks out of the mortise. Instead, keep chopping through the chunks, and if they become cumbersome, use an awl to remove them without ruining your mortise edges when prying.

So how do you know when to stop chopping?

You can use a combination square and adjust its length to match that of your tenon. Then stick it in your mortise to see how close you’re to final mortise depth. So, when your combination square bottoms out, it is time to stop chopping.

If you’re cutting a through-tenon, you’d repeat this marking and chopping process on the other side and join in the middle. But it would be best if you did not try to exit through one side.

If your mortise rectangular hole walls look perfect, concentrate now on trimming the tenon instead. You can use a shoulder plane to trim it- take some small cuts, then retest the fit. When you feel the tenon is cut and ready to join with the mortise, hit it lightly with a wooden mallet so that they can connect tightly. Besides, the more mortise and tenon joints you make, the faster and experienced you will get at it.

Great! You can now confidently make the most crucial joint in traditional woodworking. So go ahead and choose a project that has mortise and tenon joints so you can practice more.

Frequently Asked Questions on the Mortise and Tenon

1. What is the mortise & tenon joint used to make?

A mortise and tenon joint is one of the most well-known and handy means to join two pieces of wood. It’s mainly used in solid wood woodworking to connect end grain to edge grain. Besides, a mortise and tenon joint is usually at its most standard, a peg fit into a hole.

2. Why is the mortise & tenon joint the strongest?

The mortise and tenon joinery is another most attractive and one of the strongest woodwork joints due to its flush-fitting design.

3. What are the cons of a mortise and tenon joint?

The disadvantage to mortise & tenon joints is in the quality of the fabrication. If the proportions are improper, the wood can shear on either side, making the mortise & tenon joint an extremely difficult joint for DIY hobbyists to create.

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Ian Mutuli

About the author

Ian Mutuli

Founder and Managing Editor of Archute. He is also a graduate architect from The University of Nairobi, Kenya.
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