Printed from Kezuriba (kezuriba.net/en/nc/g50/)

G50

Machining center, LatheModal, group 11

Scaling cancel

⌨On machining centers

G50

On machining centers it is paired with G51 (scaling). Often an optional feature

◎On lathes: Maximum spindle speed setting (also sets the coordinate system in system A)

The same number means something different on lathes (FANUC-type G-code system A). Group 00.

G50 S_ (maximum speed) / G50 X_ Z_ (coordinate system setting, system A)

With constant surface speed control (G96), the speed keeps rising as the tool approaches the center, so always set the upper limit with G50 S before G96
To cancel, command G50 again with the machine's maximum speed (Haas)
In G-code systems B/C the same function is G92 (coordinate system setting / speed limit)

Diagram (lathe): diameter and spindle speed, constant surface speed (G96) vs constant rpm (G97)

With G96 (constant surface speed) the rpm rises as the diameter gets smaller. Without a limit set by G50 S, the rpm near the center can become dangerously high. Example: Vc = 200 m/min, limit 2000 min⁻¹.

≠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	Lathe	Meaning	Spindle speed limit onlyHaas describes G50 as a speed limit; work coordinates are handled with the G54 series
Siemens (ISO dialect)	Lathe	code	G92 in systems B/CSiemens ISO T: G50 X Z in system A is G92 X Z in systems B/C

📚Sources

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

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. — Mill Operator's Manual – 17 Mill G-Codes (online version) haascnc.com
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. — G-code, M-code, and Setting (per-code explanation pages) haascnc.com
Haas Automation, Inc. — Lathe Operator's Manual – 16 Lathe G-Codes (online version) haascnc.com
Siemens AG — SINUMERIK 802D sl/840D/840D sl/840Di/840Di sl/810D Programming Manual ISO Turning, 04.2007 Edition cache.industry.siemens.com