G AND M CODES FOR CNC MACHINING CENTERS

G AND M CODES FOR CNC MACHINING CENTERS

G Codes (Gnn)

G codes are used in CNC machining center programming to define tool movements and machining operations. The most commonly used G codes are listed below:

Common G Codes:

 G00 – Rapid positioning (Fast movement without cutting)  G01 – Linear interpolation (Cutting movement along a straight path)  G02 – Circular interpolation (Clockwise - CW)  G03 – Circular interpolation (Counter-clockwise - CCW)  G04 – Dwell (Pause before proceeding)

Coordinate Systems & Plane Selection:

 G15 – Cancel angular coordinate system  G16 – Activate angular coordinate system G17 – Select XY plane  G18 – Select ZX plane  G19 – Select YZ plane

Unit System Selection:

G20 – Inch unit system G21 – Metric unit system

Machine Home & Reference:

G28 – Return to machine home position

Tool Compensation & Offsets:

G40 – Cancel tool radius compensation  G41 – Tool radius compensation (Left)  G42 – Tool radius compensation (Right)  G43 – Tool length compensation (+ direction)  G44 – Tool length compensation (- direction)  G49 – Cancel tool length compensation

Workpiece Offsets & Referencing:

 G50 – Cancel scaling mode  G54 - G59 – Select different workpiece coordinate systems

Drilling & Tapping Cycles:

 G73 – High-speed peck drilling cycle  G74 – Left-hand tapping cycle  G76 – Precision boring cycle  G80 – Cancel drilling cycles  G81 – Basic drilling cycle  G82 – Drilling cycle with dwell at the bottom  G83 – Deep hole drilling cycle (Peck drilling)  G84 – Tapping cycle

Turning & Thread Cutting Cycles:

 G90 – External/internal turning cycle (Single pass)  G92 – Thread cutting cycle  G94 – Facing cycle (Parallel to X-axis)

Speed Control Modes:

 G96 – Constant surface cutting speed  G97 – Constant spindle speed

Feedrate Modes:

 G98 – Feedrate in mm/min (inches/min)  G99 – Feedrate in mm/rev (inches/rev)

M Codes (Mnn)

M codes are miscellaneous functions that control auxiliary machine operations.

Common M Codes:

 M00 – Program stop  M01 – Optional program stop  M02 – End of program (For single-part production)  M03 – Spindle rotation CW (Clockwise)  M04 – Spindle rotation CCW (Counter-clockwise)  M05 – Stop spindle rotation ? M06 – Tool change  M08 – Coolant ON  M09 – Coolant OFF  M30 – Program end and return to start  M98 – Call a subprogram  M99 – End of subprogram

Important Notes:

 Leading zeros in G and M codes (e.g., G01 vs. G1) are optional and do not affect program execution.  G and M codes must be used in correct order for proper execution of CNC machining processes.  M00 & M01 difference: M00 stops the machine always, while M01 only works when optional stop is enabled.