What's inside
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A door hinge recess, or mortise, needs to be deep enough for the hinge leaf to sit flush with the door edge or jamb. Too shallow, and the hinge stands proud and forces the door out of alignment. Too deep, and the hinge side pulls in, leaving a gap or making the door bind. The reliable hand-tool method is to establish a clean perimeter, remove the waste in controlled layers, and use a depth reference instead of judging by eye.
Tools and materials
You need a sharp chisel, a marking knife or sharp pencil, a combination square, a steel rule, and a hammer or light mallet. A 1/2-inch chisel is a useful general size for most residential hinges; a 3/4-inch chisel is faster for clearing waste, while a 1/4-inch chisel is better for cleaning tight corners.
A sharp bench chisel set is usually a better buy than a single oversized chisel. You can use the larger blade for bulk removal and the smaller one for corners. A cheap chisel is fine if its back is reasonably flat and the edge will take a clean bevel. A badly ground, soft-edged chisel will make this job harder regardless of price.
| Tool | Best use | Trade-off |
|---|---|---|
| Marking knife | Clean, precise layout lines | More accurate, but slower to set up |
| Sharp pencil | Quick layout and visible reference marks | Faster, but the line is wider and less exact |
| Bench chisel | Paring and controlled chopping | Versatile, but needs a mallet for heavy waste removal |
| Router plane | Checking and refining a flat, consistent bottom | Excellent control, but unnecessary for one or two hinges |
A combination square helps transfer the hinge position from the old door or jamb. For several doors, a hinge mortise gauge can speed up repeatable marking, but it is not essential for a normal repair.
Set the target depth
Measure the hinge leaf thickness with a steel rule or calipers. Common residential butt hinges have leaves roughly 1/16 to 1/8 inch thick, but do not assume. The finished recess should normally leave the hinge leaf flush with the surrounding wood. On a painted door, you may need to account for paint buildup, but do not deliberately bury the hinge to compensate for thick paint.
Mark the target depth on the chisel by wrapping a strip of masking tape around the blade. Set the tape slightly above the required depth—about 1/32 inch is useful—so you can sneak up on the final surface without cutting past it. A depth gauge or marking knife can also make a reference line across the waste, but tape is quicker for a single door.
Mark the hinge mortise
Place the hinge in its correct position and mark around it with a sharp knife. Keep the hinge barrel aligned with the door edge, and make sure the hinge leaf is oriented correctly before marking. Mark the top and bottom positions with a square. The usual door layout leaves about 5 to 7 inches from the top of the door to the upper hinge, about 10 inches from the bottom to the lower hinge, and a centered third hinge on heavier doors. Match the existing jamb whenever possible.
Score the long grain lines first, then deepen the marks with a second pass. A knife line severs the surface fibers and reduces breakout. If using a pencil, keep the line on the waste side and mark clearly; do not let the pencil line become your cutting boundary.
Remove waste in controlled stages
Start with the chisel bevel facing into the waste and the flat back toward the part you want to preserve. Hold the chisel about 1/8 inch inside the layout line and make a series of shallow vertical cuts across the mortise. Space them roughly 1/8 to 1/4 inch apart. These cuts divide the waste and prevent a long chip from tearing past the boundary.
Next, use light mallet taps to remove the ridges between the cuts. Work across the grain where possible, and keep the first pass shallow—about 1/16 inch. Do not drive the chisel to full depth in one blow. Deep chopping creates leverage against the end grain and can split the door edge, especially on pine, fir, or a hollow-core door stile.
After the bulk is out, switch to paring. Hold the chisel with both hands, blade nearly flat, and push it forward to level the bottom. Pare from the center toward the perimeter rather than levering against the edge. Leave the taped depth mark visible and take thin shavings until the bottom is close to uniform.
Keep the bottom consistent
Test-fit the hinge frequently. Place it in the recess, lay a straightedge or the chisel back across the surrounding surface, and check for rocking or gaps. A hinge that rocks usually has a high spot under the barrel or a ridge along one edge. Remove only the high area; do not deepen the whole mortise to cure one lump.
At the final stage, make overlapping paring cuts in the same direction. Keep the chisel flat and avoid digging its corners into the bottom. If you have several hinges to fit, a small router plane is useful for shaving high spots to a repeatable depth. It is overkill for a single hinge, but it can pay for itself when fitting a run of doors.
Common mistakes and fixes
If the mortise is too shallow, remove thin layers and retest. If it is slightly too deep, a thin veneer or card shim under the hinge leaf can correct it, but a deep recess may require a properly fitted wood patch. Do not rely on extra-long screws to pull a proud hinge into place; that distorts the hinge and often causes binding.
Breakout at the ends usually means the layout line was not cut deeply enough or the chisel was driven toward the edge. Re-score the boundary, then work from the edge toward the center. A ragged corner can be cleaned with a narrow sharp chisel, using the knife line as the stop.
Finally, install the screws only after the hinge sits flat. Drill small pilot holes centered in the screw holes, drive the screws evenly, and check the door before tightening fully. Consistent depth matters, but a clean perimeter and a flat bottom matter just as much.