Vintage Mortise Lock Service: what to note first

The knob flops loose on its spindle and never springs back to level. When you turn it the latch pulls in, but you have to push the knob back yourself, and lately the latch has started staying inside the door instead of catching.

Worth answering before the call

How many keys do you have, and do any of them work? Do you own the home or rent it, and who should receive the keys? Is the trouble worse with the door closed than with it open?

What if the case is too worn to repair?

Then a replacement case goes into the existing pocket. Reproduction mortise cases are made in the common vintage sizes and backsets, and a modern mortise case with a cylinder fits many old pockets with minor trimming. The locksmith measures the case height, depth, backset and trim spacing before ordering, aiming for the new case to drop in with the original knobs and plates going back on, though a small pocket trim or fixing change is sometimes needed. Cutting the door for a different kind of lock is the last choice.

Why does my knob turn without moving the latch?

Most often the square hole in the hub inside the case has rounded with age, or the spindle has worn, so the knob turns a good way before it grips. Loose knob set screws produce the same slack. Less often a latch spring has broken and the latch is simply sitting inside the door. All of these are corrected during service by replacing the spindle and screws, bushing or replacing the hub, or fitting a new spring.