The Most Efficient Tool for Removing Mortise Cylinders
Commercial locksmiths come across this problem frequently: A mortise cylinder in an Adams Rite lock mechanism won't pick and/or has been damaged so that a key cannot be made. Or an existing key fails to work because the cylinder's plug is past saving and full of debris. You can't just use a large pair of pliers to force it to unscrew because the lock has a spin ring protecting it from that.
The A116 (actually, A-1 #16) mortise cylinder removal tool is the answer. I've used mine a great many times and it's never yet failed to get the mortise cylinder out of the lock body quickly, cleanly and without doing thread damage (we all know how fine those threads are!). It uses a key blank which you insert into the lock and the tool is slipped over the protruding key. From there it becomes a long lever, and you simply apply turning force counter clockwise to force the mortise cylinder to unscrew, breaking off the tiny set screw that normally prevents this action. Super simple, super effective.