Carriage lock will not turn

[WyoRob]

I have a Mark V, circa 1977. The carriage lock is stuck, the carriage slides but the lock handle will not turn more than about and 1/8 of a revolution. It is bound up somehow, any suggestions?

[edma194]

Rust or some kind of gunk on the screw is a possibility. You can tilt up into drill press mode to examine the screw from the underside of the carriage (back side when it's tilted up). Some lubricant may help free it up. You need to remove the carriage from the way tubes and clean the threads. If it's bad enough you need to remove the lock handle and replace the screw and/or the locking wedges to fix this problem.

[DLB]

Just a short addition to Ed's answer: If you get to the point where you need to remove the lock handle it is an important note that it is Left Hand threads. More obvious is that there is a roll pin (aka spring tension pin) through the handle and rod that needs to be driven out first. I don't have a Model 500 carriage handy, but IIRC the threads are also accessible from the outside on the carriage and you'll want to apply penetrating oil in all locations if possible.

- David

[WyoRob]

Thanks, I will give it a try