CNC Programming Handbook

This archive collects practical introductions to the principal elements of CNC machine programming. Code meanings and supported functions vary among machines and controls, so always confirm commands against the programming manual for the specific equipment.

G-Codes List for CNC Machine Programming

G-codes are preparatory commands that place a CNC control into a particular operating mode. Common examples include rapid positioning, linear and circular interpolation, plane selection, work offsets, tool compensation, drilling cycles, and absolute or incremental positioning.

• G00: Rapid positioning
• G01: Linear interpolation
• G02 and G03: Clockwise and counterclockwise circular interpolation
• G54–G59: Work-coordinate offsets
• G81–G89: Common drilling and boring cycles
• G90 and G91: Absolute and incremental positioning modes

M-Codes List for CNC Machine Programming

M-codes control miscellaneous machine functions such as the spindle, coolant, tool changes, program stops, and subprograms. Frequently used commands include M03 and M04 for spindle rotation, M05 for spindle stop, M06 for an automatic tool change, M08 and M09 for coolant control, and M30 for program completion and reset.

Machine-specific M-codes are common. Some controls also restrict a block to one M-code, making the machine manual the authoritative reference.

Letter Codes for CNC Machine Programming

Letter addresses identify the type of information supplied by each word in a program block. Typical addresses include X, Y, and Z for axis positions; F for feed rate; S for spindle speed; T for tool selection; and I, J, and K for arc-center data. Their exact interpretation can depend on the active mode and controller.

Basic Programming Terms and CNC Structure

A CNC program is organized from small elements into progressively larger structures:

1. Character: A letter, number, or symbol.
2. Word: An address letter paired with a value, such as X2.500 or F12.0.
3. Block: A line containing one or more program words.
4. Program: An ordered collection of blocks that directs the machining operation.

Understanding this structure helps machinists read, write, troubleshoot, and safely edit CNC programs.