Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 436)

Using Chamfers and Corner Radius
Chapter 16
16-6
An error is generated if an attempt is made to change planes between
blocks that are chamfer or corner radius blocks.
,C and ,R must be programmed in blocks that contain axis motion in the
current plane. If they are programmed in a block that does not contain
axis motion in the currently active plane, the control will generate an
error.
,C and ,R may not be programmed in a block that contains any of the
following:
Any fixed cycle G codes
Any Dwell commands
Thread cutting blocks
Programmable zone G codes
The system installer determines in AMP the resolution of the ,C and ,R
words for both inch and metric programming. Refer to documentation
prepared by the system installer for details.
END OF CHAPTER