Cleaning a Mortice Lock

The latch on one of our doors wasn't springing back properly. Rather than being allowed to fix it I was told to fit another one. I inadvertently brought one that was too deep for the existing cutout so ended up stripping and cleaning the old one any way. A temporary saving of nearly £30

Having with drawn the lock assembly from the door, access is gained to the workings by undoing 3 screws and removing the cover plate. This lock is at least 16 years old possibly more, the problem was simply but probably only temporarily fixed by stretching the 2 coil springs on the left. I could have left it at that but seeing the swarf and grease under the key mechanism I thought a more thorough clean was in order

The dog of the spring bolt is held in place by a single screw and can be fitted either way up depending on which way the door swings and can be removed and refitted without opening up the lock as there is an access hole in the side plate I forgot to photograph. Remove the 2 springs first then two parts of the spring bolt lift out of the lock body.

The leavers for the dead bolt just lift off their pivot pin, note I have numbered each one prior to removal so they go back in the right order put them back in the wrong order you will need to make a new key but that is a different instructable.

The grey disc driven by the key is what actually drives the dead bolt across. It is only zinc alloy in this lock and the swarf is from where it has worn on the leavers and where it passes through the side plates of the lock this will ultimately need replacing, once this is remove the dead bolt its self lifts out.

I removed the bulk of the grease and swarf with a small screw driver blade then wiped the rest out with a couple of cotton wool pads soaked with lighter fluid. I also wiped the other components down in the same manner

Ideally I'd have preferred to have use wheel bearing grease, how ever all I had to hand was Vaseline so that had to do.I applied a thin coat to the pivot for the leavers and the R shaped spring the back surface of the dead bolt, both sides of the cam disc driven by the key as well as its pivot points. then a smear on the back of each lock leaver before it was fitted.

Fitting the leavers requires putting the spring int the housing first then twisting the leaver into position so it slides down the pivot shaft the springs are quite weak so this is easy to do.

Similarly grease the surfaces of the spring bolt mechanism that rub on the lock case before you fit them fit the springs after the bolt sections it is a 2 handed job hence no photos. Refit the side plate and do up the retaining screws refit the spring bolt dog making sure you get it he right way around. Test the key in the lock and that the spring bolt operates correctly then refit to the door.