Rockwell Automation 8520 9/Series CNC Lathe - Manual (Page 530)

Tool Tip Radius Compensation (TTRC)
Function
Chapter 21
21-46
The new offset is activated. TTRC is able to compensate for this new
diameter by modifying the saved jogged path. This path is modified so
that the new tool cuts the same part as the old tool. The absolute position
of the machine will, therefore, be different on the return path from what it
was when jogging away from the part.
This jogged path is adjusted when you press the button
to return from the jog retract. As soon as you press the
button, the control generates a move that offsets the current tool position
by the necessary distance. This distance is determined as the necessary
distance the tool where would have to be positioned so that the exact same
jog return paths can be used to return to the part and still have the
end-point be offset from the original position by the difference in the cutter
diameter.
CAUTION: Make sure that this offset path will not cause any
collisions with the part or the machine fixtures. The position of
the tool when the tool change in jog retract is made should be a
safe distance from the part and machine fixtures.