I agree Spock. It does make sense that it could be a limit switch. Do you have the same machine? A sharp sv2412? Anyways, I will be running it today and I am sure it will hang. I will try Neil20's suggestion of banging around where limit switches are and see if that might be it. I think before that, I will take a good look at the Z axis limit switch that I can see. Lets work together on this one and see what we can find out ?