Please talk to me about Mach 3 tool ofsets.

Mine work however I am confused about one aspect.

This video https://www.youtube.com/watch?v=IAY6M4Q7fIE shows that a Master Tool is set at zero (against an arbitary plane, defined by a bar in the chuck) and all others tools are set against this. I understand this principle, its the way I use my mill offsets.

However, what I am not sure about is how to ensure that the machine 'knows' where X is say 0 or 10mm from the centre line.

The way I have done mine is to home my machine and set all tools from this point. My DRO will therefore say '20mm' and give me a 20mm stock if I cut along that plane (both diameter mode).

The problem is that the limit switches do not repeat 100% and whilst its reasonably accurate, I am not 100% getting the same diameters once the machine is rehomed.

I could use some form of a dialguage and reference of this (for X). Thoughts?

The other option is to home the machine once, then never again. Instead of homing it I should use G Code to 'go to home' but not use the limit switch. Assuming the machine is powered down and restarted with the turret in this location, it should repeat however as I use steppers (not servo), this is not perfect. Any replacement of a tool / tool tip or need to rehome means that my 'diameters' are no longer 100%.

I find that then resetting the diameter size (John Saunders does similar) needs you to cut a part manually, then measure it and then do some sums to get the offset correct. I find this tedious and long winded. Is there a better way?

Thanks