So for G76 to work I have to have some way of sending a signal to Mach3 telling it how fast the spindle is turning, is that correct? I thought that if I programed in the spindle speed, and then set my VFD to get that speed I would be good to go. Right now I have a MachTach tachometer installed which gives me spindle speed but I am not sure if I can feed this info to Mach3. If I am on the right track here what is a good simple way of getting RPM into Mach3? Thanks.