A hinge mortise is the shallow cut made in the edge of a door and the door jamb that mirrors the size and thickness of the door hinge. The hinge mortise allows the hinge to be mounted flush with the jamb and door so the door will close properly.
Hinge mortises on a door are often cut by machine with a router and straight bit, but you can cut mortises by hand using a hammer and chisel as well. To do a good job cutting mortises, the chisel needs to be razor-sharp.
To cut hinge mortises on a door:
- Screw the hinge to the door or jamb.
- Score around the outline of the hinge with a utility knife.
- Remove the hinge from the door or jamb.
- Position the chisel on the scored line with the chisel perpendicular to the door or jamb and the bevel side of the chisel facing toward the mortise.
- Lightly tap the chisel with a hammer around the perimeter of the mortise to deepen the scored line.
- Use the chisel to make a series of cuts 1/8” apart and the depth of the hinge along the length of the mortise.
- Hold the chisel flat and use it to clean out the waste, so the mortise is the same depth as the hinge.
- Screw the hinge to the door and jamb, so the top of the hinge is flush with the door edge and door jamb.
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Danny Lipford: Now, installing a door at your house is fairly easy, but to recess hinges like this is a little more of a challenge.
Joe Truini: That’s right, Danny. Most mortises are routed out, but here’s an alternative method. Screw the hinge directly to the edge of the door, and then mark its outline with a utility knife.
Remove the hinge and use a chisel to chop out around the outline. Just remember to keep the bevel end of the chisel facing toward the waste area, so you wind up with a nice, crisp line. And then hold the chisel perfectly vertical, and make a series of cuts about an eighth-inch apart all the way across the waste area.
Then turn the chisel . . . hold the chisel flat, with the bevel facing up, and scrape out all the waste wood. To finish up, hold the chisel bevel down and smooth out the bottom of the mortise.
Danny Lipford: Now, this is an exterior door, so we’ll be using three hinges on this installation. But if you have an interior door you’re installing, two hinges is usually sufficient.