What you would do is Open MachTurn then set the X, Y and Z to same step/dir pins as you have on the mill. Motor tuning etc would be the same as well. You would then just have to mount the tool in the vice and work in the spindle and move the Y until it was spot on centre. Your X and Z would act the same as a mill. If you have Home switches then you could have a Home Off Value for both X and Y and that would mean when you commanded to go to X zero Y Zero the tool would be exactly spindle centre but for that to work each time you used MachTurn you would need a means of setting the tool and vice to exactly the same position each time. After that there would be no use for the Y in any code, you would only programme for X and Z axis.
Hood