How to Cut a Mortise with a Drill

Over draw the lay out lines a little so they are not lost during the cutting process.

Draw line 1/4" inside the end as locations for the 1/2" drill holes.

Draw lines 1/2" in from each side as guide lines for the 1" drill.

Drill 1/2" holes at corners.

Notice the 1/2" holes overhang the sides but not the ends of the mortise. These holes cut the end grain and make waste removal from the mortise much easier then without them. If this was a straight mortise (instead of a brace) there would be 1/2" holes at all four corners.

Using the guide lines, remove as much wood as possible from the mortise with the 1" drill. Drill about 1/4" deeper then needed. It may be necessary to score the end layout lines (with chisel or knife) before drilling to prevent the surrounding surface from chipping. To cut the 45 deg. end, drill progressively shallower holes.

Remove waste from the mid line of the mortise.

Drive the chisel down the end face of the mortise.

Mortise with the mid line cleaned out and end face cut (on the left). Notice how the 1/2" holes resemble mickey mouse ears.

With the mid line of the mortise cleaned out and the end grain cut by the 1/2" mickey mouse ears the waste splits easily off the side faces. This is where the mickey mouse ears save a huge amount of time and effort. Cut the mortise wide enough to remove the side lay out lines. Timber framing is not cabinet making. Timber framing joinery should fall together.

Drive the chisel down the 45 deg. face of the mortise. If most of the waste is not already removed this will be very difficult.

The mickey mouse ears are covered up by the brace shoulders. This applies to any joint as long as the tenon is shouldered on both sides.