The XR20-W calibration system from Renishaw (Hoffman Estates, IL) wirelessly measures the an gular position of rotary axes to within ±1 arc second for testing the accuracy of lathes, multi-axis ma chine tools, mill-turn machines, trunnion tables, and spindles. It works in conjunction with XL-80 or ML10 laser interferometers, and combines the readings of the rotary calibrator and laser to determine positioning errors in axes under test. Off-axis rotary software allows it to be used even when it cannot be positioned directly on the rotary axis under test. The software calculates true position and records axis performance and errors when compared to the intended target. It attaches to a rotary axis via a flexible mounting ring assembly, and is centered within ±1 mm (0.04") using a visual aid. Flexible mounting options include an adapter plate for rotary tables with unsuitable center recesses, and a chuck adapter for lathes.