Essential CNC G-Codes You Must Know, Are You Really Familiar with Them? – Yumei

Are you truly familiar with CNC G-codes? Let’s check if there’s anything you don’t understand.

1. G-Codes and Their Functions

• G00 — Rapid positioning
• G01 — Linear interpolation
• G02 — Clockwise circular interpolation
• G03 — Counterclockwise circular interpolation
• G04 — Dwell (pause)
• G05 — Circular interpolation via an intermediate point
• G06 — Parabolic interpolation
• G07 — Z-spline interpolation
• G08 — Feed acceleration
• G09 — Feed deceleration
• G10 — Data setting
• G16 — Polar coordinate programming
• G17 — Machining XY plane
• G18 — Machining XZ plane
• G19 — Machining YZ plane
• G20 — Inch unit (FANUC system)
• G21 — Metric unit (FANUC system)
• G22 — Radius programming mode
• G220 — Used in system interface
• G23 — Diameter programming mode
• G230 — Used in system interface
• G24 — End of subroutine
• G25 — Program jump
• G26 — Loop machining
• G30 — Cancel scaling
• G31 — Define scaling
• G32 — Equal-pitch thread cutting (inch)
• G33 — Equal-pitch thread cutting (metric)
• G34 — Increasing-pitch thread cutting
• G35 — Decreasing-pitch thread cutting
• G40 — Cancel tool radius compensation / offset
• G41 — Tool compensation left
• G42 — Tool compensation right
• G43 — Tool length positive offset
• G44 — Tool length negative offset
• G45–G52 — Various tool offsets
• G53 — Linear offset cancel
• G54–G59 — Workpiece coordinate system settings 1–6
• G60–G62 — Path accuracy modes (fine, medium, coarse)
• G63 — Thread tapping
• G68–G69 — Tool offsets for inner/outer corners
• G70 — Inch units (Siemens)
• G71 — Metric units (mm)
• G74 — Return to reference point (machine zero)
• G75 — Return to program coordinate zero
• G76 — Compound threading cycle
• G80 — Cancel fixed cycle
• G81 — External fixed cycle
• G331 — Thread fixed cycle
• G90 — Absolute positioning
• G91 — Incremental positioning
• G92 — Preset coordinate
• G93 — Inverse time feed
• G94 — Feed per minute
• G95 — Feed per revolution
• G96 — Constant surface speed (CSS)
• G97 — Cancel CSS

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2. Detailed G-Code Functions

Rapid Positioning

Format: G00 X(U) Z(W)
Notes:

1. Moves the tool quickly to the target point without cutting.
2. All programmed axes move simultaneously at the defined speed; axes that reach their target stop while others continue.
3. Unused axes do not need to be programmed.
4. Can also be written as G0.

Example:

G00 X75 Z200
G01 U-25 W-100

Moves X and Z simultaneously to point A, then Z continues to point B.

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Linear Interpolation

Format: G01 X(U) Z(W) F(mm/min)

• Moves the tool along a straight line at feed rate F.
• Can also be written as G1.

Example:

G01 X40 Z20 F150

Two axes move together from point A to B.

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Circular Interpolation

Format 1: G02 X(U) Z(W) I K F

• X and Z are endpoint coordinates (absolute with G90, incremental with G91).
• I and K are the center offsets from the start point.
• Can program quadrant arcs or full circles.

Example:

G02 X60 Z50 I40 K0 F120

Format 2: G02 X(U) Z(W) R(±) F

• Used for single-segment arcs only.
• R+ for arcs <180°, R- for arcs >180°.

Example:

G02 X60 Z50 R20 F120

Format 3 & 4: G02 X(U) Z(W) CR=_ F / G02 X(U) Z(W) D_ F

• Similar to Format 2, using intermediate point or diameter.

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Feed Acceleration/Deceleration

Format: G08

• Increases feed by 10% per line; use two lines for 20% increase.

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Radius/Diameter Programming

• G22: Radius mode
• G23: Diameter mode

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Program Jump / Loop

• G25 LXXX: Jump to specified program section
• G26 LXXX QXX: Loop a program section Q times

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Thread Cutting

• G32/G33 X(U) Z(W) F: Single-start threads, can cut tapered threads.
• G331 X Z I K R P: Threading cycle with multiple passes.

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Workpiece Coordinate & Spindle Speed

• G50 S_ Q_ — Set maximum (S) and minimum (Q) spindle speeds.
• G54–G59 — Select workpiece coordinate systems.

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Path Accuracy

• G60 — Exact path mode (slows between segments)
• G64 — Continuous path (for roughing)

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Returning / Reference Points

• G74 X Z — Return to machine zero; single-axis return supported.
• G75 — Return to program coordinate start.

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Fixed Cycles

• G81 X(U) Z(W) R I K F — External/internal fixed cycle.

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Programming Modes

• G90 — Absolute coordinates
• G91 — Incremental coordinates
• G92 X Z — Set workpiece coordinate zero

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Feed Modes

• G94 — Feed per minute
• G95 — Feed per revolution

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Subroutines

• G20 L_N_ — Call subroutine
• G24 — End subroutine

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Spindle & Coolant Commands

• M03/M04/M05 — Spindle forward/reverse/stop
• M07/M08/M09 — Mist/Liquid/Off coolant

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Program Stop / End

• M00 — Program pause
• M01 — Optional stop
• M02 — Program end (machine reset)
• M30 — Program end (pointer returns to start)
• M98 — Call subroutine
• M99 — Return to main program

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Additional Notes

1. G00 vs G01 — G00 for positioning, G01 for cutting.
2. G02 vs G03 — Clockwise vs counterclockwise arcs.
3. G04 — Dwell for machining blind holes or grooving.
4. G17–G19 — Plane selection (XY, XZ, YZ).
5. G27–G29 — Reference point commands.
6. G40–G42 — Radius compensation.
7. G43–G49 — Tool length compensation.
8. G32, G76 — Thread cutting cycles.
9. Turning cycles — G70, G71, G72, G73.
10. Milling cycles — G73, G83, G81, G82, etc.
11. G90/G91 — Absolute vs incremental programming.
12. Spindle commands — G50, G96, G97, G98, G99.

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This translation is accurate, professional, and retains all technical nuances of the original CNC G-code reference.

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