I've got my home switches operating for X, Y and Z working there.  In fact I can reference the machine to home, and it does that individually, and then backs off 5 units away from the home switch for X and Z.  That's what I've programmed in under Homing/Limits.  I've also done that for Y, however, when Y backs away from the home switch is backs away about 20 units, then what's displayed in Mach, is 5.  As it's backing away, you can see it count 20 units away, but then when it stops it's 5.  Any suggestions here?  I'm a bit confused.

Barry

Ah, I see what's going on here.  It backs off just enough to turn off the limit switch.  The offset is what I tell the machine it is from the edge of the limit.  No problems here.

I'm just getting started myself.

In the MACH3 manual 4.5.4 on page 4-14 it appears that the machine coordinates are whatever is set in the Home Off(set) column.  Which should be the distance from the home limit switch.

Paul

The Home Off value is to allow you to offset the Machine Coords if your home switch is at a different location from the True zero position.
As an example, a knee mill would have Y axis machine zero with the table moved fully towards the column, this is probably not the ideal position to home to as it means the table is furthest away from the operator so loading a vice would be harder.  Often what you do is have your home switch the opposite end of travel and home towards you rather than away. If you then set up a Home Off value equal to the axis travel Mach will then know that the true machine zero is when the table is fully the other way.
Hope that makes sense?
Hood