emc g92

i have the emc rc46 bdi on a small lathe. i jog the machine into
position and make the first cut. i then measure the part and set the
machine position with g92. this does not seem to work for me. i have
searched the web and found a lot of references to g92 and g54-g59.
maybe g92 does not work on my machine or maybe i am confused. how can
i reset the position in emc to match the position of the tool bit?
thank you