Fixed abrasive polishing method and apparatus

The method of polishing a rigid magnetic disk substrate comprising:

• rotating said magnetic disk substrate about a substantially horizontal axis;
• applying a water soluable, low viscosity liquid vehicle to the disk substrate surfaces to be polished;
• rotating a pair of confronting annuli of non-friable, high density polyurethane foam impregnated with in excess of 50% by weight of classified hard particles, said annuli having an inner diameter greater than the difference of the inner and outer radii of the disk substrate annular surface to be polished;
• and
• positioning said pair of confronting annuli at opposite sides of said disk substrate about a common axis parallel to the axis of said disk substrate rotation, whereby the inner diameter of said annuli extends across the disk substrate annular width to be polished and maintaining a contact pressure of at least 5 pounds per square inch between said annuli and said disk substrate for a predetermined period of time.

The method of polishing a rigid, metal magnetic disk substrate comprising:

• applying a water soluble, low viscosity liquid vehicle to the disk substrate surface to be polished;
• rotating a circular polishing media of non-friable, non-rigid high density polyurethane foam impregnated with in excess of 50% by weight of classified hard particles and mounted on a rigid backing plate, said media having a diameter greater than the difference of the inner and outer radii of the substrate annular surface to be polished;
• and
• placing said rotating polishing media in contact with said disk substrate with the axis of said substrate and said polishing media parallel and relatively displaced such that the polishing media diameter extends across the substrate annular width to be polished, whereby said polishing media rotates relative to said annular substrate and induces rotation of said substrate.