Dealing with old mortise locks

Exactly how have they stopped working? I found that mine didn't work when I bought the house, but I removed all the excess paint off of them, and then cleaned and lubed then, then they worked just fine. Can you take it apart? The trick is to get enough greas on the sliding parts (and I used regular automotive wheel bearing grease).

Mine are completely rusted.

Is it possible to remove the rust, sand until smoothed, then grease? And yes the ones at Home Depot don't exactly match mine either, which is why I didn't try to use them (different measurements) maybe if you tried a different supplier you might be able to find some decent ones (Home Depot carries poorest quality available of a lot of things).

I would take it apart and wire brush/wheel everything and then put it back together an lube it up really well. Do you have an architectural salvage company near you? You could get a replacement from them most likely. or

I suspect that the OP is attempting to use those crappy "Franklin" (Made in China) aftermarket ones they sell at Home Depot. I brought one of my existing ones to the store and the measurements didn't match up. I say try again, preforably through the mail. Don't alter the door, buy the right part.

A wire wheel in the place of a grindstone on a bench grinder is wonderful for removing rust. It makes a lot of things look like new. Cleans up more than 90% of what I have with rust or paint on it. There is also naval jelly but that hasn't worked so well or me.