Hi Ken,
if you don't have home switches, which I guess is quite likely as you are still experimenting, then if you hit <Ref All> the machine will
reference itself to its current location, sometimes called 'Home in Place'. That will mean that the machine co-ordinates of the current location
will be 0,0,0. The axis LEDs will go green, which informs you that the machine is referenced.
Referencing means MACHINE COORDINATES. They are what Mach (3 or 4) uses as native positioning but are not usually used by us, mere humans
that we are. For us we would jog to one corner of the material and the zero each axis. Note that 'zeroing' an axis is different to 'referencing' an axis.
When we 'zero' an axis or axes we are setting WORK COORDINATES. Work coordinates are much more user friendly, its easy to visualize 2 inches
from the left corner and 2 inches up from the left corner of a piece of wood you are working on say. Work coordinates are intimately related to offsets.
The offsets are the translation from Machine Coordinates to Work Coordinates and are used by Mach but seldom by us. Further if you follow the
procedure...reference (home) the machine, jog to the start of the job and then 'zero' the machine the offsets are automatically defined and stored.
Craig