Auto-homing without setting origin?

Z endstop pins on the arduino, one to the plate, one clamped on the tool.

@Joakim

So to use X & Y endstops and touchplate, would you set the zero location in CAM file to be the same offset that your part is relative to your machine origin?

In other words, would you set your XY origin in CAM to be 3" to the left and 3" down from where the part actually sits. Then when you press play, it goes to the correct corner of the part and starts cutting?