G AND M CODES IN CNC LATHE MACHINES

G AND M CODES IN CNC LATHE MACHINES

 

G Codes

G codes are used in CNC programming to control machining movements and operations. The range of G-code numbers is G00 – G99.

Basic G Codes

· G00 – Rapid movement (non-cutting motion)

· G01 – Linear interpolation (cutting motion)

· G02 – Clockwise (CW) circular interpolation

· G03 – Counterclockwise (CCW) circular interpolation

· G04 – Dwell (pause)

· G20 – Inch measurement system

· G21 – Metric measurement system

· G28 – Return to reference point

· G31 – Skip function

· G32 – Thread cutting

· G34 – Variable pitch threading

Tool Compensation & Speed Control

· G40 – Tool radius compensation cancel

· G41 – Tool radius compensation (left)

· G42 – Tool radius compensation (right)

· G50 – Maximum spindle speed limitation

· G54 - G59 – Workpiece coordinate system

Machining Cycles

· G70 – Finishing turning cycle

· G71 – Rough turning cycle (longitudinal)

· G72 – Face turning cycle

· G73 – Profile rough turning cycle

· G74 – Peck drilling cycle in Z-axis

· G75 – Peck drilling cycle in X-axis

· G76 – Multi-pass threading cycle

· G80 – Canned cycle cancel

· G83 – Deep hole drilling cycle

· G84 – Tapping cycle

Advanced Machining Functions

· G90 – Outer/inner cylindrical turning cycle (single pass)

· G92 – Threading cycle

· G94 – Face turning cycle

· G96 – Constant surface speed

· G97 – Fixed spindle speed

· G98 – Feed rate in mm/min

· G99 – Feed rate in mm/rev

 

M Codes (Mnn)

M codes are auxiliary functions in CNC programming that assist machining operations. They are represented as M + two-digit number (e.g., M00, M03, M08).

Basic M Codes

· M00 – Program stop (halts execution regardless of optional stop switch status)

· M01 – Optional stop (stops if optional stop switch is active)

· M02 – Program end (used for single-part machining)

· M03 – Spindle on (clockwise)

· M04 – Spindle on (counterclockwise)

· M05 – Spindle stop

· M06 – Tool change

Coolant & Auxiliary Functions

· M08 – Coolant on

· M09 – Coolant off

· M19 – Spindle orientation

· M30 – Program end and return to the beginning

· M98 – Subprogram call

· M99 – Subprogram end

Optional Formatting Rules in CNC Programming

In CNC programs, leading zeros (0) before numbers in G and M codes are optional. Whether they are included or omitted does not affect the functionality of the program.

For example:

· M0 (without a leading zero) is equivalent to M00

· G1 is the same as G01

 

Usage of M Codes in CNC Programming

· M0 › The machine stops and waits for operator intervention. It resumes only when the Cycle Start button is pressed. This is useful for inspection or reorientation of a workpiece before continuing.

· M1 › Optional stop. If the Optional Stop switch is ON, the machine stops when it encounters M1. Otherwise, it continues executing the program.

· M30 › Ends the program and automatically returns to the beginning.

 

Practical Applications of M0 & M1

- M0 for Workpiece Repositioning

· If both ends of a workpiece need machining, M0 stops the machine after the first side is finished.

· The operator flips the part and presses Cycle Start to continue machining the second side.

- M0 for Deep Hole Drilling

· When drilling soft materials, chips can clog the drill.

· The machine stops at M0, allowing the operator to clean the drill before resuming the process.

- M1 for Selective Stopping

· Unlike M0, which always stops the machine, M1 stops only if the Optional Stop switch is ON.

· If the switch is OFF, the program continues uninterrupted.