Rotary Table
A rotary table is a precision workholding and positioning device that rotates a part around a fixed axis for cutting, drilling, or indexing at exact angular intervals. In CNC machining, it functions as an added rotational axis—typically the 4th axis—enabling indexed positioning and continuous coordinated motion with X, Y, Z. This reduces setups and improves positional accuracy across multiple features.
On the shop floor, a rotary table transforms a three-axis mill into a four-axis workhorse. Instead of unclamping, flipping, and re-indicating a part for each side, the machinist programs the rotary axis to index or synchronously contour, slashing setup time and eliminating re-fixturing errors. Common applications include circular bolt patterns, side drilling, spoked features, and multi-face prismatic parts. The critical setup variables are centerline alignment, table concentricity, fixture overhang, part mass, and clamping torque. Mechanically, these tables use a servo or stepper motor with a gearbox or direct drive, demanding tight backlash control and repeatability under load. Proper controller configuration for rotary scaling and backlash compensation is essential to maintain angular accuracy across production runs.
Is a rotary table the same as a 4th axis?
Not exactly. A rotary table is the hardware; “4th axis” refers to its role in the CNC control system as an additional programmed rotational axis.
When do you use indexing versus continuous rotation?
Indexing is used for discrete face-to-face operations like drilling and milling at set angles, while continuous rotation is used for helical features, engraving, and coordinated contouring.
Why does a rotary table improve accuracy?
It reduces re-clamping and re-indicating, which removes one of the largest sources of cumulative setup error in multi-face parts.