CNC Machining G-Codes, M-Codes, Tools, and Measurement

G0

Rapid positioning (fast movement to a location)

G1

Linear interpolation (straight-line cutting)

G2

Circular interpolation clockwise

G3

Circular interpolation counterclockwise

G4

Dwell (pause for a specified time)

G28

Return to machine home position

G43

Activate tool height offset (compensation)

G44/G49

Cancel tool height offset

G50

Set maximum spindle RPM for constant surface speed (CSS)

G54-G59

Work Coordinate Systems (WCS) settings

G80

Cancel canned cycles (e.g., drilling cycles)

G90

Absolute programming (coordinates relative to origin)

G91

Incremental programming (coordinates relative to current position)

M0

Program stop

M1

Optional program stop

M2

Program end

M3

Spindle on clockwise

M4

Spindle on counterclockwise

M5

Spindle off

M6

Tool change (e.g., T1 M6)

M8

Coolant on

M9

Coolant off

M30

End program and return to main program

CSS (Constant Surface Speed)

Automatically adjusts spindle RPM based on tool diameter to maintain consistent cutting speed.

Fixed RPM

A constant rotational speed maintained by the spindle.

Direct RPM

The actual rotational speed of the spindle, measured in revolutions per minute (RPM).

FPT/IPT (Feed per Tooth/Inches per Tooth)

The thickness of the chip removed by one cutting edge of the tool per revolution, typically ranging from 0.0005" to 0.010".

Roughing Endmills

Tools with serrated cutting edges for rapid material removal.

Ballnose Endmill

An endmill with a half-round sphere ground on its end, used for 3D contouring.

Radius Endmill

A flat endmill with radiused corners to reduce sharp edges.

Chamfer Endmills

Used to produce a bevel on the workpiece edge.

Tapered Endmills

Used to mill angled surfaces without tilting the machine head.

Shell Endmill

A multiple-flute hollow cutter mounted onto an arbor.

Face Mill

A multiple-cutting-edge milling cutter with replaceable inserts.

Toe Clamps

Allow a part to be held down against the table by gripping only on its edges.

Toggle Clamps

Provide quick clamping and release of workpieces.

C-Clamps

Used to secure workpieces to the machine table.

Milling Vises

Similar to drill press vises but made to higher precision for milling operations.

Collets

Precision tool holders that grip the tool or workpiece.

Spring Collets

Accurately ground cylindrical sleeves for holding tools or workpieces.

Step Collets

Used to grip short workpieces whose diameters are too large to fit within standard spring collets.

Expanding Collet

Includes an integral arbor instead of a hole.

Live Center

Mounted in a bearing cartridge and freely rotates with the workpiece while the mounting shank stays stationary.

Dead Center

Used in the headstock spindle and has no rotating parts.

Gage Blocks

Extremely accurately sized blocks with very smooth surfaces used for part inspection or to check the accuracy of other precision measuring tools.

Pin or Plug Gages

Cylindrical rods with very accurate diameters used to check hole dimensions.

Taper Plug Gages

Single-ended plug gages that match a particular rate of diameter change.

Snap Gages

C-shaped gages used to check external dimensions.

Radius and Fillet Gages

Used to check outside corner and inside corner (fillet) radii.

Telescoping Gage

Shaped like a "T" with two arms that expand when the locking screw is loosened.