HEIDENHAIN TNC 320 User Manual page 218

Overlapping contours
By default, the TNC considers a programmed contour to be a pocket.
With the functions of the contour formula, you can convert a contour
from a pocket to an island.
Pockets and islands can be overlapped to form a new contour. You can
thus enlarge the area of a pocket by another pocket or reduce it by an
island.
Subprograms: overlapping pockets
The following programming examples are contour
description programs that are defined in a contour
definition program. The contour definition program is
called through the SEL CONTOUR function in the actual main
program.
Pockets A and B overlap.
The TNC calculates the points of intersection S1 and S2 (they do not
have to be programmed).
The pockets are programmed as full circles.
218 Fixed Cycles: Contour Pocket with Contour Formula