Printed from Kezuriba (kezuriba.net/en/nc/g43/)

G43

Machining center, LatheModal, group 08

Tool length compensation + (adds the offset)

⌨On machining centers

G43 Z_ H_ (in the same block as G00/G01)

H is the tool length offset number. Matching it to the tool number is common, but it can be different
Command it together with the Z move, and activate it well above the workpiece
A mistyped H number leads straight to a crash. Always check the G43 H block right after a tool change

Diagram: Tool length compensation: spindle gauge line and H

G43 Z_ H_ moves with the length H from the spindle gauge line to the tool tip added, so the tool tip arrives at the commanded Z (example of the common setup that measures tool length from the gauge line). A mistyped H number leads directly to a crash.

◎On lathes: (Not used on typical FANUC-type lathes. The tool offset is selected by the last 2 digits of the T code)

The same number means something different on lathes (FANUC-type G-code system A).

On lathes, the tool number and offset number are specified together with a 4-digit T code such as T0101 (6 digits on some machines) (Mitsubishi lathe material, MHLW material)
Haas lathes have G43 (group 08), but offsets are normally applied with the T code

≠Differences between controls and machines

The same code can be written or assigned differently depending on the CNC control and the machine builder. Always check your machine’s manual.

Source	Machine	Item	Detail
Haas	Machining center	Notes	On NGC software 100.21.000.1100 and later, tool length compensation is always activeOn newer Haas software, compensation stays active unless G49/H00 is explicitly commanded, and it is updated automatically at tool change

📚Sources

The meaning shown agrees in at least two sources (agreement confirmed). Explanations are written in our own words.

Mitsubishi Electric — The Basics of CNC Machining Programming (for Machining center) e-Learning material (PDF) mitsubishielectric.com
Siemens AG — SINUMERIK 802D sl/840D/840D sl/840Di/840Di sl/810D Programming Manual ISO Milling, 04.2007 Edition (6FC5398-7BP10-0BA0) cache.industry.siemens.com
Haas Automation, Inc. — G-code, M-code, and Setting (per-code explanation pages) haascnc.com
Haas Automation, Inc. — Mill Operator's Manual – 17 Mill G-Codes (online version) haascnc.com
National Institute of Standards and Technology (NIST), USA — The NIST RS274NGC Interpreter – Version 3 (NISTIR 6556, 2000) nvlpubs.nist.gov
Saitama University, Faculty of Engineering, Department of Mechanical Engineering, practical training — Machining center program 2019 (training NC program O19-0101, with comments) jisshu.mech.saitama-u.ac.jp
Mitsubishi Electric — The Basics of CNC Machining Programming (for Lathe) e-Learning material (PDF, BNP-C8027-688) mitsubishielectric.com
Ministry of Health, Labour and Welfare (MHLW), Human Resources Development Bureau, Office of the Councillor for Skills Evaluation — Human resource development manual using the practical exam tasks of the Grade 3 Skilled Worker Test: CNC lathe work (March 2018) waza.mhlw.go.jp
Haas Automation, Inc. — Lathe Operator's Manual – 16 Lathe G-Codes (online version) haascnc.com