On closing Mach4 spindle switches on!!

[V8kid]

Your BOB does not support Spindle except in Relay mode / the relay switches it off and on/ . So no PWM, no 0-10V. forget about that

Hence in ESS manual is explained how to properly set the spindle in that mode.

It could be done with additional board but easier and cheaper will be probably to buy a better BOB, best with integrated transformer or converter for the 0-10v/ 0-5v ,most spindles /VDFs/ support both modes

And about that ON/Off problem. Remove power to the board and try connecting the relay outputs to see if problem persists. So you remove board from equation or problem is in the relay of the board, or the way you have programed that relay in Mach3 outputs

Thanks Boyan so the BOB will not support spindle speed I think I'll try Bill Caldwells method using Modbus RTU rather than replacing the BOB as the usb to RS485 converter is only a fiver on eBay.

Re the other advice I confirmed it is settings in Mach4 but what settings? I have already followed the manual ( your link was to mach3 and the screens are quite different) to no avail.

Will see how I get on with Modbus RTU

Cheers