Neither of the lathes I have worked on seem to need a cross-slide lock. When I am turning on the Monarch I can see that the Y DRO value never changes. The same applies on the carriage, although it does have a lock there. Do you need one since it's a lighter lathe or has more vibration? It appears that there is a screw on the slide that need to be tightened when using the taper attachment, and it does seem to act as a lock as well. The other lathe is at school and is a Harrison 14"