Hi, Drad
The simplest way. find the two wires in your torch head that turn on the torch, remote them from the box to a relay NO contacts on your IO Board.
Use the Output 2 for Spindle (M3), Enable Output 2 and assign a Pin #, port#, Active low to check mark or X depending on board wiring, in
config, ports & pins, Outputs.
One of many ways.
Hope this Helps, Chip