Where to drill to open a mortise lock?

To drill open a mortise lock means creating a substitute "shear line". For those who are not locksmiths, a shear line is created when the proper key is inserted into the lock and the top and bottom pin tumblers line up flush to turn the plug.

Using a 1/4 inch carbide tip drill bit, drill about an 8th of an inch above the keyway. It's advisable to use a center punch so the drill bit doesn't "walk" and damage the whole cylinder.

Start drilling slow at first so the drill bit can get a "bite" and not fly off and cause you injury or damage the door. Then apply pressure to drill through the plug but don't push too hard or the bit might break off in the lock. When you feel a slight jolt, it means you drilled through a pin.

Keep going until you've drilled through all 5 pins. Do not drill too deep or you'll damage the whole lock mechanism. Then stop drilling and use a pick or scratch awl to scape the remaining pins out of the chambers and you can turn the plug with a screwdriver and it will unlock the door.