Dating antique furniture locks

Most older and antique furniture locks work on the simple idea of a key moving a bolt through the lock and into the adjoining frame member.The key usually fits over a center pin of a given size and rotates around it.These locks are most common on early 20th-century pieces and on inexpensive reproductions, and are commonly used as replacement locks by inexperienced restoration “experts.” The purpose of a lock, of course, is to keep someone out of a private place.But since most locks are designed only to keep honest people honest, a determined trespasser can almost always find a way in.The top selvage is visible, but so is the back or lock plate of the lock on the inside of the drawer front.Also, usually visible on a half mortise lock are the screws or nails that hold the lock in place.

A half mortise lock is exactly as it sounds—half exposed.The key must not only be the right size to move the bolt forward and back, it must be the right size to compress the spring and release the bolt so it can move.Most bolts have two notches, one in the locked position and one in the unlocked position.The levers must be aligned in a perfect line to allow the bolt to pass but since their thickness is random and hidden, figuring out a cut pattern is very difficult.

This lock requires notches to be made on the bottom of the key blade rather than on the face of the blade and is much more difficult to fabricate. Apparently, the 19th-century English had more of a need for security than we did.

This is one case where if you don’t have the key, don’t worry about it.