Apparatus for manufacturing substantially spherical objects to a high degree of roundness

An apparatus for imparting a substantially uniform spherical shape to the sealing surface of a ball valve flow control ball having diametrically opposed trunnions formed thereon coincident with a longitudinal axis through the geometric center thereof, and having a flow control port bored therethrough transverse to the longitudinal axis, comprising:

• means for rotating the ball about its longitudinal axis;
• a grinding head rotatable about a second axis perpendicular to the longitudinal axis of the ball and coincident with the geometric center thereof;
• means for rotating said grinding head;
• a plurality of shafts mounted with said grinding head and extending therefrom radially from a common point on said second axis, said shafts rotatable about their longitudinal axes;
• means for rotating said shafts about their said longitudinal axes;
• a grinding wheel mounted on each of said shafts a predetermined radial distance from said second axis, said wheels each having a beveled grinding surface facing said second axis for tangentially engaging the surface of the ball and each being rotatable with said shaft;
• and
• means for positioning said ball in grinding engagement with said beveled grinding surfaces of said grinding wheels with said second axis perpendicular to the longitudinal axis of the ball while simultaneously rotating the ball about the longitudinal axis thereof, rotating said grinding head about said second axis, and rotating said grinding wheels and said shafts about the longitudinal axes thereof.