Although a chisel mortise is best known for its use in a joint known as mortise-and tenon, it is a great way to countersink a hinge plate in a door. With the right tools and instructions you can chisel a mortise in less than five minutes.
Step 1 - Draw the Mortise Outline
For a door with 3 hinges you'll need to chisel 6 mortises: 3 on the door and 3 on the door jamb. Place each door hinge on the door edge that will fit against the door jamb when the door is closed. With a pencil draw a line on the door, following the edge of the hinge.
Step 2 – Cut a Slot
Hold your chisel edge on the pencil line, bevel side toward the door edge. Tap the chisel end with your hammer or mallet, cutting a slot to the depth that will equal the thickness of the hinge.
Step 3 – Chisel Out the Mortise
Hold you chisel flat against the surface of the mortise you wish to remove, bevel edge down. Then, tap with a hammer or mallet until you've removed the wood, leaving the surface of the mortise flat and even.