...though replacing the BLDC motor on the mill with a servo was precisely because it fitted the same highly restricted space envelope, for the same power, for less than the price of the replacement BLDC control board which I'd blown twice (okay, factor in the new pulley and belt and it was probably a bit more total cost), but it removed all the analogue uncertainty of spindle speed control or any third-party interfaces (that spindle, also step/dir control). Plus (and some might cringe at this) - the option of a spindle lock