Well I have taken a quick look around and not seen an answer maybe you guys could help.  I am looking to make long smallish diameter  shafts on my 12x39 smithy lathe.  Is it possible to only use the y-axis (crosslide) axis stepper encoder and just run the x-axis apron with standard headstock feed and an encoder/balllscrew  or glass scales for position?  These could be fine cuts and probably slow and i dont know how critical backlash would play although the lathe is very new and tight. I am working on better computer skills so thorough explainations needed, sorry. Thanks for listening ya'all. Freddy57

Hi. This is not a clear question at least for me that my primary language is not english. I am sure that if you make it simpler, myself or other is able to help.

Whether it's a reasonable thing to do, I don't know, but one way you could do this is to put a switch on the machine, connected to the Mach3 PROBE input, to tell you when you've reached the end of the cut.  Then do the actual cut with a G31 move.  You'd have to start the spindle first, and reverse the spindle to move back to the starting point.   As long as you only cut one direction, backlash should not matter.  I suppose you could also do in in units/rev mode, and do away with the switch.  The trick will be coming up with a foolproof means of determining the end of cut, before you run into the chuck.  Or, just cut away from the headstock, and stop it manually after you run off the end of the part.

Regards,
Ray L.

To state more clearly.  I am using this lathe 12x39 to turn pool cue shaft tapers.  The cutting tool is a wood router mounted to the y-axis crosslide which would use a standard stepper encoder motor on linear rails.  This axis would not require a great deal of force.  However, the problem in actuating the apron or x-axis is the high torque loading and also high cost of components to perform such a task.   For tapering there is no reversal or pause within the full toolpath cycle.  My hope was to use the headstock and leadscrew locked in time to handle the apron travel.  The router is always running so there is no necessary rotational engagement speed. My thoughts are that at the end of one direction of travel , stop the lathe,increase the cut, and without disengaging the leadscrew and simply reverse spindle and leadscrew rotation with one switch.  I'm sure easier said or typed than done and dont know if mach3 can be configured. Thanks to all of you guys. Freddy57

I think that the backlash on the leadscrew of a "common" lathe will be the most difficult to handle, also the decelerating and accelerating time would be critical so that the taper will not hit bottom.
Maybe to much tunning for a correct job, but if there are many pieces to be done, why not ?