Marking the Hinges

• A mortise cut into a door is shallow and perfectly fits the hinge. New doors ship with placement templates, but generally the outside edge of a hinge is installed 5 to 7 inches from the top of the door or 10 to 11 inches from the bottom. Match hinge placement with other doors in the room. When replacing a door, lay the older door on its replacement to mark where the new hinges will be cut. Lay the hinge on the stile (edge) of the door, and scribe around the outside of the hinge with a utility knife or awl. To mark the depth of the mortise, put a level on the stile, hold the hinge underneath, and mark below the hinge. Repeat the process for each hinge on the door. When replacing a door, you'll be able to use the existing mortises in the door frame, but for new installations, measure the door to mark the hinges in the frame. Leave 1/8-inch clearance between the top of the door and the frame and 1/2-inch clearance between the door and the lower plate or floor.
  
  

Cutting the Mortise

• A sharp woodworking chisel is the best tool to cut mortises. New chisels must be sharpened with a grinding wheel or sharpening stones before use. Gently tap the chisel with a plastic or rubber mallet to score the outer line of the mortise on the stile.Then make parallel cuts with the chisel about 1/4-inch apart across the grain of the wood. Don't cut below the marked depth of the hinge. Place your chisel on the depth line, and push it into the door to remove the sections of wood you have mortised. You might be able apply hand pressure, but use the mallet if necessary. Test-fit the hinge into the recess, and remove wood until the metal is flush with the stile of the door. If you have cut too deeply, shim behind the hinge with cardboard or wood shims. Once the hinge fits correctly, mark the openings, then drill the screw holes with a self-centering bit. Test-fit the door and hinges into the frame before installing the screws.