Not good enough. For a given TPI the ratio of the spindle speed to that of the leadscrew must be *exactly* equal to the ratio of two particular integers. This can be done with electronics but it can't be done by manually setting a speed control.Digital ratation counter in manual mode for different threads and then mark those speeds on the dial indicator of the new motor controller.
To make threads you need to make multiple passes, backing out and backing up after each pass. The next pass has to be lined up exactly in the cut of the previous pass. I don't understand how that can be accomplished without a mechanical link between the spindle and the leadscrew. I've seen electric powered feeds before but they only worked for turning, not threading.Digital ratation counter in manual mode for different threads and then mark those speeds on the dial indicator of the new motor controller.