EMC one last question !!

I got the bdi disk. I installed it okay. I wired up the home and
limit switches. with the help of you folks I got out of e-stop and
have been having a blast homing and cruising around with it. I have
however got 1 last problem. I am used to windows based, or dos based
controllers. with these I would jog in to the edge of the stock, find
my stock zero, and then zero the axis by means of some button and
with xyz zeroed, away I would go. I home with emc and this sets
MACHINE zero for all the axes, but, my question is; after I have
jogged to my STOCK 0,0,0 how do I set the axes to zero so that the g-
code can start from part 0,0,0 rather than machine 0,0,0.
I know this should be intuitively obvious but for some reason I
just cant get the missing part


Thanks again for the help in advance
For the sake of knowledge the macine is a metric sherline. It uses
180 oz in steppers from maxnc, but I have built my own driver box
with sd200 drives. The ram from the 2000 mill now bolts to a custom
turret mount which also has a nema23 mount on the back so I can drive
y with the stepper mounted on the backside. with 1mm pitch screws it
runs a little over 5 mm/sec rapid and makes 75 lbs of linear force at
the table. the turret has lateral and linear gusset rods to stabilize
against wobble in flycut ops and it allows for micro-tramming the z
axis for trueness
pictures to follow when I get a camera