What is the difference between machine zero and work zero in CNC machining?

Machine Zero is a permanent, factory-set physical coordinate established by the machine builder that serves as the absolute reference origin for all machine axis travel, soft limits, and automatic tool changer locations. When a CNC machine is powered on and homed, its internal encoders register their absolute positions relative to this fixed global origin (G53). Machine Zero never changes during operation and remains entirely independent of the workpiece, vise, or tooling setup mounted on the table.

Work Zero, defined through Work Coordinate Systems (WCS) such as G54 through G59, is an adjustable, user-defined datum point set directly on the raw stock, part feature, or fixture reference plane. Machinists establish Work Zero using edge finders, touch probes, or dial indicators to align the machine coordinate space with the CAM model origin. Programmed toolpaths and part dimensions execute strictly relative to this Work Zero coordinate. When paired with modular tooling systems anchored by drawbars, spigots, or pull studs, Work Zero offsets can remain permanently stored in the CNC control, allowing operators to swap pre-fixtured pallets in and out without probing part datums between cycles. Because syntax, custom macros, and auxiliary hardware commands vary across controller manufacturers and machine tool builders, programmers and operators must always consult their specific machine manual to verify exact code definitions and functions before running a program.