Home switch in the middle of Z axis

[frijoli]

The factory home switch on my Southbend is hard mounted in the middle of the Z travel. Is there an easy way to use this to home, and then move away in the + direction for 4 inches and then set machine zero?
The X axis is in the normal location.

[cncsnw]

Yes, you can add an incremental move in between the M92 line (which finds the switch) and the M26 line (which sets zero).

You will want to be sure you have a working overtravel switch at the plus end, so that when you inadvertently start the homing sequence without first jogging to the left of the home switch, it will stop with a "limit tripped" error instead of damaging something.

It could be made a little more foolproof if you modify the trip ramp to ensure that the home switch remains tripped all the way from the middle of travel to the plus limit. That way the control can tell which half of travel it is in by the state of the switch, and can start off moving minus to clear the switch if needed.

[frijoli]

Excellent. I had a suspicion that was the way it worked, but never tested.

Thanks!