[mactec54]

I understand that mach3 has 4 decimal places on the dro, it's irrelevant, it can actually use up to 12 decimal places (maybe it's 10), 4 is just what's shown on the dro, that doesn't mean it can send partial steps to a servo drive. The limitation for resolution is based on steps per unit. The minimal output it can give (actual movement) is limited by the distance of a single step. In most machines, running in inch mode, moving 0.0001 is not usually a problem. On my machine for example, I have 5mm pitch screws and 2000 micro step, comes out to about a tenth of linear axis movement so moving .0001 in inch is fine, however I do most of my work in metric, so mm for units. In this case a single step is .0025mm (400 steps per unit in mm) and I assure you, mach3 does not allow a smaller move than that since I only have 400 steps per mm, it would if i had finer resolution motors and higher step per unit. I can take a video to demonstrate if you like. If I set the step jog to .0001mm, I have to give 25 clicks of the handwheel before mach3 will actually send a microstep to move the motor. Obviously servos can have finer resolution than steppers, but a minimum move is still limited by a single step. I'm sure any machine on servos and most on steppers has a fine enough step to move .0001 inches, but we are talking much smaller moves, .005 "degree" at the servo shaft, not .0001" (inch linear) on a linear axis which is a MUCH larger move. Mach3 will not output a partial step, if 1 step is larger than .005 "degrees" at the servo shaft, mach3 will not do it. You would need 72000 steps per rev minimum (revolution, not inch) to command the servo to make that small of a move. Im not sure where we are getting mixed up, i think it's because you are thinking linear inches, in which case .0001 inch moves is not usually limited by a single step. I'm talking much smaller moves.

Are you comparing Steppers to Servos there is no comparison between the 2 systems ( 1 ) click of the handwheel would mean the servo would move what ever that resolution was set at inch or metric makes not difference

Even it something was to move .005 degrees you would not have anything you could verify the measurement with, the mechanic's that you posted for your build would be the deciding factor not what you are driving it with

I have a Megatorque motor that I use for a 4th axes it has a 20Bit Encoder which is over 1million CPR and it can move and hold any position you can dream up, these motors only do 500 RPM though