How To Chisel a Mortise

In layman's terms, the mortise is a slot where another piece is inserted. It forms a joint when connected with a tenon, a projection on the end of a piece of wood. Together, they are called the mortise-and-tenon joints. It is popular with woodworkers because of its simplicity and strength. Even today, the use of the mortise-and-tenon joint is still commendable, especially in the world of framing. Its principal use is in the construction of door and window frames of our homes and other structures. As we know it, the best tool for door and window framing is a chisel and a mallet, and as a rule, the mortise should be the first cut since it is the basis for the measurement of the tenon. Thus, learning how to chisel a mortise should be the first thing to do. The steps below will help you how.

  1. Layout the mortise by using a pencil. Mark it properly to make sure that the layout is seen. You can use a ruler or tape measure for specific measurements. You can also use the ruler to rule straight lines in forming the layout.
  2. Choose a chisel that has the exact width as the mortise. If it is not possible for you to find one, you may want to adjust the dimensions of the joint in order to match the chisel that you are going to use. You can also sharpen the chisel before use to make sure that the blade is sharp.
  3. Use a clamp to firmly hold the work piece into the workbench. This is important so that the work piece won't slip and then cause you to tap outside the layout formed.
  4. Hold the chisel upright with the hand that you are most comfortable with. Let's say, with your left hand assuming that you are right-handed. Grip it with comfort in a 90 degrees vertical position while holding the mallet with your right hand. Give a firm blow towards the handle of the chisel. Do the same process until you reach the depth desired for your mortise. Always keep track of the pattern as you strike the handle of the chisel. The beveled edge, same as your knuckles, should face away from you while holding a firm grip to the chisel handle.
  5. Remember that in square-sided cuts, the bevel must be faced toward the waste side.
  6. Point the chisel away from your body at an angle of 45 degrees before tapping the chisel. Do the same thing until the mortise is formed.
  7. Chip the sections with the use of your hand to make smooth finishing cuts.
  8. Use sand paper to smoothen the texture of the wood.

After the mortise is formed, you are now ready to make the tenon. As mentioned earlier, mortise serves as the basis for the measurement of the tenon, thus, using the mortise would determine the size of the tenon. Just to make sure, the initial size of your tenon must be a little bit fatter than the cavity of the mortise. Try fitting after a few rough measurements and make sure not to have a sloppy fit, rather, snug a perfectly tight fit.


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