Abstract
This paper describes the stability of water-lubricated conical bearings with spiral grooves for high speed spindles. The bearings are intended to apply to spindles for drilling small holes of printed circuit-boards. Pressurized water is first fed to the inside of the rotating shaft and, then, supplied to spiral grooves through feeding holes. Therefore, water pressure is greatly increased at the outlets of feeding holes due to the centrifugal force by shaft rotation. In addition, water pressure also increases by viscous pumping effect of spiral grooves. The threshold of instability is theoretically predicted and calculated results are compared with experimental data. It was found that conical bearings treated in this paper have excellent stability at high speeds.
