An evaluation method of radial accuracy for hydrostatic air spindles considering radial movement of the rotating center

In this paper, we observed radial movement of the rotating center of a hydrostatic air spindle and have proposed an evaluation method of radial accuracy including radial movement of the rotating center. Our results are summarized as follows: (1) porous type spindles experienced limited radial motion during single revolutions. However, excessive rotating center movement was noted in comparison with inherent compensation restrictor types. (2) In the horizontal position, radial movement of the rotating center of an air spindle was excessive in comparison with the vertical position. (3) Repeatability of radial movement of the rotating center was within 0.1 μm. (4) As for radial movement of the rotating center, radial accuracy of the air spindle was significantly higher than the motion of one revolution.