Glossary of CNC Terms

Your go-to reference for mastering CNC terminology

Whether you’re evaluating machines, reading spec sheets, or training new operators, CNC terminology can feel like a foreign language. This glossary breaks down the most essential terms so you can speak CNC with confidence—whether you’re on the shop floor or making strategic decisions.

A–C

Axis A direction along which the CNC machine moves—typically X (left/right), Y (forward/back), and Z (up/down).
Backlash The small amount of lost motion due to gaps between mechanical parts, often corrected in software.
Ball Screw A precision screw mechanism that converts rotary motion into linear motion with minimal friction.
CAM (Computer-Aided Manufacturing) Software used to generate toolpaths and instructions for CNC machines.
CNC (Computer Numerical Control) A system that automates machine tools using programmed commands.
Coolant Liquid or gas used to reduce heat and friction during machining.
Cycle Time The total time required to complete one machining operation or part.

D–H

Datum A reference point or surface from which measurements are taken.
Drill Bit A cutting tool used to create cylindrical holes.
End Mill A cutting tool used for milling operations, typically with cutting edges on the sides and bottom.
Feed Rate The speed at which the cutting tool moves through the material.
Fixture A device used to securely hold a workpiece during machining.
G-Code The programming language used to control CNC machines, specifying movements and operations.
HMI (Human-Machine Interface) The control panel or screen used by operators to interact with the CNC system.

I–M

Interpolation The process of calculating intermediate points to create smooth toolpaths.
Jogging Manually moving the machine along its axes using the control panel.
Kerf The width of material removed by a cutting process.
Lead-In / Lead-Out The path the tool takes before entering and after exiting the cut to ensure smooth transitions.
Machine Zero The fixed origin point of the machine’s coordinate system.
M-Code Commands used to control machine functions like coolant, spindle on/off, or tool changes.
Mill A machine tool used to remove material by rotating a cutting tool.

O–S

Offset A value used to adjust the position of tools or workpieces for accurate machining.
Post-Processor Software that converts CAM data into machine-specific G-code.
RPM (Revolutions Per Minute) The speed at which the spindle or cutting tool rotates.
Spindle The rotating component that holds and drives the cutting tool.
Step-Over The lateral distance between passes of the cutting tool during milling.
Surface Finish The texture and smoothness of a machined surface.

T–Z

Taper A gradual decrease in diameter along the length of a tool or hole.
Toolpath The programmed route the cutting tool follows during machining.
Tool Wear The gradual degradation of a cutting tool due to use.
Tolerance The allowable deviation from a specified dimension.
Work Coordinate System (WCS) A user-defined coordinate system used to position the workpiece.
Workholding Devices used to secure the workpiece during machining.
Zero Point The starting point for machining operations, often set by the operator.