Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 488)

Tool Control Functions
Chapter 20
20-4
The control offers a function called tool length offset for offsetting tool
paths. The tool length offset is usually equal to the difference between the
bottom face of the tool and the gauge line. Put the tool length offset into
memory in advance. This function lets the control use the same program
to produce the same workpiece regardless of the length of the cutting tool.
Figure 20.2 illustrates the reference points used for deriving a tool length
offset.
Figure 20.2
Tool Length Offset
cutting tool
gauge
line
Program G44 if
- Geometry values
+ Wear values Program G43 if
+ Geometry values
- Wear values
There are three G codes, G43, G44 and G49, that are used when
programming tool length offsets. To know when to use them, see below:
G43
If the sum of the tool geometry and the tool wear is a positive offset value,
program G43.
For example:
If the values for tool offset no. 1 are:
Tool Geometry +3.0000
Tool Wear -0.1000
The tool offset is: +2.9000