Rotary table for a coordinate measuring machine and method of determining the axis of table rotation.

摘要

A rotary workpiece support table (12) for a horizontal arm coordinate measuring machine (10) having a retractable datum ball (144) for determining the axis of rotation of a table top plate (36) on a table base (40). A frictional drive mechanism (38) has a drive wheel (72) urged into engagement with a perimeter surface (74) and rotates the table top plate (36), with a counterforce roller (98) neutralizing the side loading on an air spindle (116). The table base (40) is positioned on a machine base (30) and spacer (32) by a rotational connection (46) and a diametrically opposite block and cam follower connection (48) to avoid the effects of differential thermal expansion between the table base (40) and the machine base (30) and spacer (32).