CNC Glossary

Compensation applied to the tool or work zero to correct wear, geometry or positioning.

Program coordinate origin, set with G54–G59. Every X/Z coordinate is measured from this point.

Physical reference point of the machine. Where the axis goes on G28 / homing.

Radius of the lathe insert tip. Without G41/G42 it causes profile errors on tapers and arcs.

Speed at which the tool moves against the part. Usually mm/rev on a lathe; mm/min on a mill.

Spindle rotation speed, in RPM. Controlled by S and M03/M04/M05.

Actual linear speed of the cutting edge against the part, in m/min. Basis for computing RPM.

Device that holds the workpiece on the lathe.

Rotating tool holder on the lathe carrying multiple tools, indexed by command (T0101, T0202…).

Command that runs a complex sequence (G71 roughing, G76 threading…) with a few parameters.

Straight-line move at a controlled feed — G01.

Arc move controlled by G02 (CW) or G03 (CCW), with R or I/K.

Code that stays active until replaced by another in the same group (G01, G96, F, S).

Code valid only in the block where it appears (G04, G28).

Block called by M98 and ended by M99. Useful for repeating patterns.

Cutting fluid. M08 turns it on, M09 off.

Helical profile cut with G32 (linear) or G76 (canned cycle).

Turns off, or activates left/right correction for the tool-nose radius.

A single line of a CNC program, usually starting with N.

Program executed from the start, usually identified by O####.