Mortise and Tenon Joints: Parts, Types, Strength, and How-to


Mortise and tenon joints are a very strong form of joinery used in woodworking with many variations to strengthen the joint. In this article, I will first go over the anatomy of the mortise and tenon joint, types of mortises, and how to create one yourself.

Directory

  1. Mortise and tenon parts
  2. Types of Mortise and Tenon joints
  3. Mortise and Tenon Strength
  4. What size should my mortise and tenon joint be?
  5. How to make a mortise and tenon joint

Mortise and tenon parts

When creating a mortise and tenon joint, one piece of wood will be the mortise and the other piece will be the tenon.

The tenon always goes into the mortise.

Source- https://www.woodworkersjournal.com/mortise-tenon-know-parts/

Types of Mortise and Tenon joints

The tenons of stopped, or blind, mortises do not fully penetrate the wood. Through mortise and tenon joints have tenons that fully penetrate the wood.

There are many variations with of stopped mortise joints as well as through mortise and tenons. Additionally, most variations can be stopped and through mortise and tenon joints

Here are the most common mortise and tenon joints..

  1. Stopped Mortise and Tenon
  2. Through mortise and tenon
  3. Double mortise and tenon
  4. Twin Mortise and Tenon
  5. Wedged Mortise and Tenon
  6. Tusk mortise and tenon
  7. Pegged Mortise and Tenon
  8. Haunched Mortise and Tenon

Stopped mortise and tenon

The tenons of stopped, or blind, mortises do not fully penetrate the wood.

Technically, Mortise and Tenon joints of other variations can also be a Stopped Mortise and Tenon joint.

With this joint, I am referring to the single, rectangular tenon.

Through mortise and tenon

A Through Mortise and Tenon joint has a tenon that fully penetrates the wood of the mortise.

Just like the stopped mortise, there are other variations to the mortise and tenon joint that can be classified as a Through Mortise and Tenon. For this joint, I am referring to the single, rectangular tenon.

Through Mortise and Tenon joints tend to be stronger than Stopped mortise and tenon joints due to more joinable, or glueable, surface area.

Twin mortise and tenon

The Twin Mortise and Tenon joint has two separate mortises and tenons.

These mortise and tenon joints are much stronger because of the more joinable, or glueable, surface area.

Double Mortise and Tenon

The Double Mortise and Tenon joint is much like Twin Mortise and Tenon joint. However, it does not have two distinct mortises and tenon.

The Double Mortise and Tenon joint has two connected Mortises and Tenons.

These joints result in more glueable surface area than the traditional Twin Mortise and Tenon Joint.

Important Note: Some people use Twin and Double Mortise and Tenon interchangeably. I see the Twin as two separate mortise and tenon and the Double as two connect mortise and tenons more commonly.

Wedged Mortise and Tenon

One of the key factors in a strong mortise and tenon joint is how tight the tenon fits into the mortise.

A Wedged Mortise and Tenon joint ensures that you get the tightest possible fit for your joint.

A Wedged Mortise and Tenon joint is created by cutting saw lines into the tenon. Once the tenon is fitted into the mortise, wedges are hammered into the tenon to tighten the fit of the joint.

Tusk mortise and tenon

A tusk is similar to the wedged Mortise and tenon joint in the sense of using a wedge to tighten the mortise and tenon joint.

The tenon, or tusk, is made extra long and a through mortise is created in the tenon. So you essentially have two mortises, one for the mortise wood piece, and one in the tenon.

A wedge is then placed in the mortised tenon to tighten the fit of the joint.

Pegged Mortise and Tenon

First, you will make a traditional stopped or through mortise and tenon joint. You can also make a twin or double mortise and tenon joint.

To make a Pegged Mortise and Tenon joint, you will drill dowel holes through the mortise, tenon, and the other side of the mortise.

Once you insert the dowels, you will create a tight joint with more surface area and prevent movement of the joints.

Haunched Mortise and Tenon

Haunched Mortise and tenons are created by incorporating a haunch in the tenon. The haunch not only has more surface area to increase the strength, it will also be able to resist rotational motion of the joint.

Read On

Below I will describe how to make your mortise and tenon joints stronger, what dimensions to use for mortise and tenon joints, and how to make a mortise and tenon joint.

Mortise and Tenon Strength

Mortise and tenon joints are already very strong joints in woodworking. Luckily, there are ways to make an already strong joint much stronger.

7 ways to make a standard mortise and tenon joint stronger

  1. Larger tenons, more surface area
    • The larger the tenon, the stronger the joint
    • The tenon width is strongly correlated to the strength of the joint
    • The tenon length is the second most important factor, and then the thickness
  2. Tighter joints
    • The tighter the tenon fits in the mortise, the stronger the joint will be
  3. Pegged mortises and tenon joints
    • Well assembled pegged mortise and tenon joints allow for less movement in the mortise and tenon, resulting in a stronger joint
  4. Double tenon joinery
    • Double tenons greatly increase the surface area of mortise and tenon joints. This directly increases the strength of the joint.
  5. Wedged tenon joinery
    • Wedge and tusk mortise and tenon joints have wedges that tightens the mortise and tenon joint.
    • The tighter the joint, the stronger the joint
  6. Haunched tenon joinery
    • Haunched tenons not only increases the surface area to strengthen the join, but it also is designed to reduce rotational movement in the mortise and tenon joint.

What size should my mortise and tenon joint be?

As mentioned before, the larger your tenon, the stronger your joint, given that the tightness and joinery type are the same.

However, you may not have the luxury of making the largest tenons depending on your project.

The depth of the mortise and length of the tenon should be at least 2/3rds of the mortise board width.

Additional the width of the mortise and thickness of the tenon should be at least 1/5 of the depth of the mortise joint.

Thinner and shorter tenons will not hold well.

How to make a mortise and tenon joint

In this section, I will explain how to make the most common mortise and tenon joints. The steps for each one are roughly the same.

First you will..

  1. Gather your materials
  2. Take all of your measurements and mark the wood
  3. Create the mortise
  4. Create the tenon

Important Note:

When creating mortise and tenon, you will need to know how to use hand tools like a chisel and marking gauge. You will also need to know how to use the saw and boring method of your choice. Let that be a hand saw, table saw, router, drill press, or chisel.

To learn how to use hand tools, you should check out the hand tool section of my website to find articles on using a hand saw, chisel, and marking gauge.

To learn more about power tools, you should check out the power tool section under the getting started page to learn more about using a drill press, router, and table saw.

1. Gather Materials

To make mortise and tenons, you can either use only hand tools, or a combination of hand and power tools

Materials to take measurements and mark the wood

You will need hand tools to mark the wood precisely to take accurate measurements.

  1. Marking gauge
    • There are many different types of marking gauges on the market
    • You can use a traditional marking/cutting gauge or a dual marking/cutting gauge
    • The dual gauge will make it slightly easier to measure and mark your pieces.
  2. Pencil
    • You will need a pencil to mark the wood to indicate which face goes with which wood piece
    • You will also need to mark which parts of the wood to cut off
    • Not doing so can make it easy to make simple mistakes when cutting and assembling wood

Materials to create the mortise

You can create a mortise by using hand tools, a router, or a drill press.

  1. Hand tools method
    • Chisels
  2. Router method
    • Router
    • Square router bits
      • You will need square/mortise router bits to cut the correct shape in the wood.
    • Router table or fence
      • You will need a router table with a fence or an attachable fence to your router to create straight lines
      • If you do not use a fence, you will need to cut close to the line and chisel the rest of the wood.
  3. Drill press method
    • Drill press
    • Drill bits
      • You will need large enough drill bits to bore the holes for you mortise
    • Chisel
      • While you can bore out the mortises completely, I would recommend getting close to the line and chisel the rest of the wood.

Materials to create the tenon

You can create a tenon by using hand tools, a router, or a table saw.

  1. Hand tools method
    • Hand saw
      • A rip saw is a good saw to cut most tenons.
      • Dovetail and crosscut saws are also beneficial for certain parts of the tenon and types of projects.
      • To learn more about handsaws and which one would be the best, you should check out this article.
    • Chisel
  2. Router method
    • Router
    • Square router bit
    • Router fence or table
  3. Table saw method
    • Table saw
    • Dado blade or chisel
      • To cut a tenon perfectly you will need a dado blade.
      • Dado blades have square or flat blades that allow for a flushed cut
      • If you do not have a dado blade, you can even the wood using a chisel

2. Take measurements and mark wood

Now that we have all of the tools that we need, we can take our measurements.

Source- https://www.woodworkersjournal.com/mortise-tenon-know-parts/

The steps to take measurements are as follows..

  1. Mark tenon length and mortise depth
  2. Mark tenon width and mortise length
  3. Mark tenon thickness and mortise width

Mark the depth of the tenon

To find the depth of the tenon, you want to align the wood together to see how far you want the tenon to go.

Next you want to mark a line to indicate the length of the tenon.

Mark all 4 sides for the tenon length.

After that, you will mark a line to indicate the depth of the mortise.

Mark the face of the wood for the mortises.

Mark tenon width and mortise length

Now is a good time to indicate the tenon width.

If you want to have your tenon be the width of the tenon board, then you will not need to indicate the tenon width. Your mortise length will be the length of the tenon board.

A cosmetic shoulder will have more surface area and create a stronger joint.

To mark the tenon width, adjust the miter gauge and mark the tenon width on both sides.

Align the mortise and tenon wood just like the previous step and transfer that mark to the mortise wood.

Use a square and a marking knife, or a miter gauge if it is long enough, to mark the complete line on the mortise wood.

Mark tenon thickness and mortise width

Lastly, you will use the marking gauge to indicate where your tenon will start.

You want the tenon thickness to be 1/5 of the depth of the mortise or length of the tenon.

Using a single marking gauge

If you are using a single marking gauge, you will want to mark the mortise wood now to use the same measurements.

Now you will adjust the marking gauge and mark the other side of the tenon, getting the full tenon thickness.

Use the same marking measurements to transfer it to the mortise wood piece.

Using a double marking gauge

If you are using a double marking gauge, you can mark both lines for the tenon and then transfer it to the mortise wood.

First, you will set up your first and second markers on your gauge.

You will want your mortise width, to be the at least the width of your chisel, router bit, or drill bit. Not smaller.

Next, you will mark the tenon wood.

Then, you will transfer those markings to the mortise wood.

Now you will mark the second line for your tenon thickness.

3. Create the mortise

Many people fail to make strong mortise and tenon joints because they create the tenon first.

You always want to create the mortise before creating the tenon. It is easier to fine-tune a tenon then a mortise.

As mentioned before, there are 3 ways to create a mortise. You can use a hand tools, a router, or a drill press.

Using hand tools

First, you want to mark the mortise line on your chisel. You can use a piece of tape, expo marker, or sharpie if you do mind a permanent line.

If you followed the steps, the mortise width should be the width of the chisel.

Having the flat part of the chisel facing out, line the chisel 1/8th of an inch short of the line.

It’s always better to cut too small and increase gradually.

Hammer slightly and pull back to chip off the wood.

Move the chisel backwards and repeat for the remainder of the mortise.

Once you have one layer down, repeat until you chisel down to the line marked on the chisel.

Now you can clean up the mortise by chiseling to the line.

Using a router

It is best to use a plunge router and a router fence to cut a mortise.

First, you will set the depth of the router bit to the mortise depth.

Next, you will align the router bit at least 1/8th of an inch short of the edge of the mortise.

I like to leave more space, in case of unexpected kickback or splitting.

Next, you will plunge the bit into the mortise wood little by little.

Plunging all at once can burn the wood and router bit, and possibly overheat the motor.

Lastly, you can either align the router bit to cut out the mortise perfectly or chisel the rest.

Chiseling is safer if you know proper chiseling techniques, because the router may have kickback or split the wood.

Having the router on a lower setting and knowing good router techniques can prevent this.

To learn good router techniques and common mistakes, then you should check out my article where “How to operate, tips and tricks, and common mistakes”.

Using a drill press

You will use a drill press to cut out a mortise almost identically using a router.

With the drill press, you will first want to set the maximum depth and align the drill bit 1/8th of an inch short of the mortise edge.

You will then cut out little by little until you reach the maximum depth.

A fence is not necessary for a drill press because you will have more control over where the drill bit goes.

A router is much heavier and bulky, making it harder to control.

A drill press is stationary, and you use both hands to move the wood where you want.

4. Create the tenon

Lastly, you will want to create the tenon. Luckily, if you go to this part, it is a lot easier than cutting a mortise.

First, align the mortise with the tenon markings to see if everything still aligns.

Now, you can either use hand tools, a router, or a table saw to cut the tenon.

Cut tenon using hand tools

First, you will align the saw 1/8th short from the tenon thickness line.

Then you will cut down until you are 1/8th inches short from the tenon length line.

You will repeat for the other side of the tenon, and then chisel the excess wood away.

Cut tenon using router

Using a router table to cut a tenon is the easiest in my opinion. This is because you will have both hands to move the wood.

Using a router table for a mortise is very difficult because you have to plunge the bit into the wood.

Anyways, first you will align the bit to the tenon thickness line.

Next, you will adjust the fence to cut little by little until the router bit reaches the tenon length line.

Then, you will repeat and do the other side of the tenon.

You can either adjust the router bit and repeat for the tenon width, or you can chisel that part off.

Cut tenon using table saw

Using a table saw, first you will align the blade to the tenon thickness line.

If you have a dado blade, you will be able to make square cuts until you get to the tenon length line. Then you will have a flushed tenon cut.

If you are using a regular blade, you will want to cut for every 1/4th to 1/8th of an inch until you get to the tenon length line.

Afterwards, you will chisel out the wood and clean up the cut.

Conclusion

In this article we learned what a mortise and tenon joint is and how to create a mortise and tenon joint using hand tools, a router, and a drill press.

Thank you so much for taking the time to read this article and I wish you luck on your woodworking journeys!

Rachel

My name is Rachel Blanding and I am a woodworker. I started woodworking at the beginning of the COVID-19 pandemic. I mainly create and refurbish furniture and create art. In this site I will share with you the knowledge I have gained over the years, and what worked for me and what didn't.

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