Indexer

In CNC machining and millwork, an indexer is a rotary positioning device that moves a workpiece to a specific angular position and holds it there for discrete machining operations—such as drilling, slotting, or multi-sided milling—rather than providing continuous rotary motion.

On the shop floor, an indexer is mounted as a rotary axis on a CNC machine or used as a standalone rotary table. The controller sends an M-code to command an indexed move, then waits for a completion signal before continuing the program. This setup eliminates the need to re-clamp workpieces for multi-sided jobs, preserving angular registration and reducing setup variation. In millwork, indexers are used to machine repeatable features on posts, spindles, balusters, and gunstocks. By rotating the part to exact angular increments without re-fixturing, indexers improve hole-to-hole and face-to-face repeatability, making multi-face machining practical in a single setup. The device typically achieves a resolution of 28,800 steps per revolution with an accuracy of ±0.006° per step, ensuring tight tolerance control for complex parts.

• ⚠️Angular cumulative error: Backlash or lost steps cause a few arc-minutes of drift per move; this adds up over many indexes, resulting in misaligned holes or off-pitch flats.
• ⚠️Wrong centerline setup: If the cutter centerline does not align with the rotary axis, the tool sweeps an eccentric path, producing uneven wall thickness or a walking profile as the part indexes.
• ⚠️Direct indexing beyond division limits: Using a manual indexer with a hole pattern that does not match the required divisions forces approximation, risking wrong spacing and scrap.