How to Do Mortise & Tenon Joints

Written by martha adams
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How to Do Mortise & Tenon Joints
Use a mallet and chisel to make a mortise and tenon joint. (Jupiterimages/BananaStock/Getty Images)

The mortise and tenon joint is a method of joinery in use since at least the Bronze Age. Its basic format is a square or rectangular projection (or "male" part) that fits into a matching cavity (or "female" part). In its crudest form, it joins the massive lintels of Stonehenge to their uprights, and in its most delicate connects the sides of an ancient Egyptian ivory box with intricate dovetails. The specific style of mortise and tenon joint will vary with the individual project. The tools may range from a simple hammer and chisel to modern power tools and a complex jig, but the basics of its construction are universal.

Skill level:
Moderately Challenging

Things you need

  • Mortise gauge
  • Try square
  • Marking knife
  • Pencil
  • Mallet
  • Chisel
  • Tenon saw
  • Woodworking vice
  • Safety goggles

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    Cutting the Mortise

  1. 1

    To hand-cut a simple mortise and tenon joint the full width of the wood, gather the wood to be joined and the tools you will use. Select a chisel to match the width of the mortise you wish to cut.

  2. 2

    Set the fixed spur of the mortise gauge at one side of the blade of the chisel and the adjustable spur against the other. Secure them in position. This will be used again to mark the width of the tenon, so leave it unchanged.

  3. 3

    Lay the try square on the first piece of wood at the point you wish to begin the mortise. Hold it securely in place and use the marking knife against it to mark the upper line. Measure the length of the mortise carefully and mark the lower line.

  4. 4

    Press the stock of the mortise gauge against the side of the wood with the spurs on the marked lower line of the mortise. Slide it upward smoothly until the spurs touch the upper line so that the spurs score the wood and mark the parallel sides of the mortise you will cut.

  5. 5

    Clamp the wood securely in a vice to control bounce and ensure straight, clean chisel cuts.

  6. 6

    Place the blade of the chisel against and inside the lower line of the mortise. Tap the handle with the mallet, gently at first, then with increased force as necessary to break out the waste wood in small increments. Reverse the chisel for the last cut to make the end clean and vertical.

  7. 7

    Continue to chop out the waste wood until your mortise is the desired depth.

    Cutting the Tenon

  1. 1

    Mark the depth of the tenon all the way around the second piece of wood, using the try square and marking knife. Use a pencil to emphasise the line for greater visibility.

  2. 2

    Use the mortise gauge to mark the width of the tenon at the centre of the wood from the depth line on one side, around the end of the wood and down to the line on the opposite side. Hold the stock of the gauge tightly to the wood so that the pins follow a straight line and not the grain of the wood.

  3. 3

    Set the wood end upwards in the vice and position the tenon saw inside (on the waste wood side) one of the pencil lines. Cut down the side of the tenon all the way to the depth line, checking frequently to be sure the saw is cutting vertically and cleanly. Cut the opposite side in the same way.

  4. 4

    Create the shoulders of the joint by releasing the wood from the vice, turning it 90 degrees and resecuring it in the vice. Use the tenon saw to cut inside the depth line until the cut meets the side cut you made previously and the waste wood comes free. Rotate the wood 180 degrees and cut the opposite side in the same way.

    Completing the Joint

  1. 1

    Keeping the wood in the vice so that it does not slip, use the mallet and chisel carefully to smooth any rough edges and straighten the tenon.

  2. 2

    Dry-fit your mortise and tenon joint to see if you need any fine adjustments.

  3. 3

    Secure your finished mortar and tenon joint with wedges, wooden dowels, metal dowel pins, glue, paint or natural friction, according to your needs and preferences.

Tips and warnings

  • You can make mortise and tenon joints using machines, but unless you are doing multiple matching joints, hand-cutting can be faster then setting up these machines.
  • Wear safety goggles when working with wood to avoid eye injury.

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