HEIDENHAIN iTNC 530 183
5.3 Tool Compensation
Tool radius compensation
The NC block for programming a tool movement contains:
 G41 or G42 for radius compensation
 G43 or G44, for radius compensation in single-axis movements
 G40 if there is no radius compensation 
Radius compensation becomes effective as soon as a tool is called 
and is moved with a straight line block in the working plane with G41 
or G42.
For radius compensation, the TNC takes the delta values from both the 
T block and the tool table into account:
Compensation value = R + DR
TOOL CALL
 + DR
TAB
 where
Contouring without radius compensation: G40
The tool center moves in the working plane along the programmed 
path or to the programmed coordinates.
Applications: Drilling and boring, pre-positioning.
The TNC automatically cancels radius compensation if 
you:
 program a straight line block with G40
 program a PGM CALL
 select a new program with PGM MGT.
R Tool radius R from the G99 block or tool table
DR 
TOOL CALL
Oversize for radius DR in the T block (not taken 
into account by the position display)
DR 
TAB:
Oversize for radius DR in the tool table