Abstract: Disclosed is a method for making re-sintered polycrystalline CBN compact which comprises placing sintered boron-rich polycrystalline CBN particles in a high temperature/high pressure apparatus and subjecting said boron-rich CBN particles to a pressure and a temperature adequate to re-sinter said particles, the temperature being below the reconversion temperature of CBN, for a time sufficient to re-sinter the polycrystalline CBN particles therein. The boron-rich polycrystalline CBN particles in the HP/HT apparatus contain no impurity which would interfere with the sintering process (CBN sintering inhibiting impurities) and no sintering aid material.

Abstract: An improved cyclical centrifugal machine includes a rigid support mounted above the basket of the machine, a bearing housing suspended from the support for gyratory motion, a basket-carrying spindle rotatable in fixed position relative to the housing on bearings therein, and an electric motor for bringing the spindle and basket to rotational speed. The improved centrifugal machine further includes a buffer system for resisting gyration of the bearing housing, spindle, and basket as well as a sensing system for detecting when such gyration, nevertheless, becomes excessive and for then discontinuing driving of the spindle and basket by the motor.