What is an "indexer"?

A look at the tool that allows you spin your workpiece while you mill it

“What’s this?” Is a common question students ask when they see this in the Haas VF-1 for the first time

An indexer, also known as a rotary indexer, is an accessory for a CNC mill that allows for the rotation of a workpiece around a specific axis, typically the "C" axis. This allows for the machining of complex geometries on the workpiece that would otherwise be difficult or impossible to achieve with just the standard 3 linear axes (X, Y, Z) of motion of a CNC mill.

When a machine is described as having 4 or 5 axes, it means that in addition to the standard 3 linear axes of motion, it also has additional axes of rotation. For example, a 4-axis CNC mill would have the standard 3 linear axes (X, Y, and Z) plus one additional rotary axis, typically the "A" axis. A 5-axis machine would have the standard 3 linear axes plus two additional rotary axes, typically the "A" and "B" axes. The number of axes on a machine determines the degree of freedom it has in terms of movement and thus the complexity of parts that it can machine.

Examples of indexer use

Making gears manually on a rotary table

A 4th axis on a Haas mill using a rotary indexer