Haas Mill · G-code
G43 Tool Length Compensation +
Applies the tool length offset stored in register H so Z positions are measured from the tool tip.
What G43 does on a Haas mill
G43 H tells the control how long the tool in the spindle is, so a command like Z0.1 puts the tip of the tool 0.1 above part zero. It is normally the first Z move after a tool change.
H should match the tool number — T5 with H05. G49 cancels length compensation.
G43 format
| Address | Meaning |
|---|---|
H | Tool length offset number (match the tool number) |
Z | First Z position with the offset active |
G43 example program
T5 M06
G00 G90 G54 X1. Y1. S3000 M03
G43 H05 Z1. M08⚠ Watch out
The most common crash on a vertical mill is the wrong H number: tool 5 with H04 means the control thinks the tool is a different length. Read the T and H numbers together every time.
Related codes
G43 questions
Does the H number have to match the T number?
Not technically, but it should. Mismatched H and T numbers are one of the most common causes of crashes.
Which code cancels G43?
G49.
Independent reference. Not affiliated with, sponsored by or endorsed by Haas Automation, Inc. Haas is a trademark of its respective owner. Always confirm codes against your machine's operator manual — options and settings vary by model and software version.