I found your schematic last night, couldn't remember where I first saw it, and studied it thoroughly. Bear with me as electricity is not my strong point. If I understand your logic the factory supplied for/rev switch is still used to control spindle direction. I understand the function of the two momentary switches; one for On and one for Off. Is this correct? Is the symbol in the wire between forward and reverse a diode? For info my mill is CNC but will manually be changing speed and spindle direction until I move onto phase 2. Phase 2 will be a ESS and spindle control board upgrade. Til the next onslaught of questions, thanks for your help. Tom S.