Abstract: A surface grinding apparatus in which a work piece having a plate-like, disc-like, circular or annular shape and having a flat surface and a uniform thickness, which is held by carrier plates between upper and lower horizontal surface tables confronting one another, is pressed against the upper and lower surface tables and the upper and lower surface table and carrier plates are slidably moved by different rotary actions to grind the work piece by sliding friction.

Abstract: A surface grinding apparatus including a plurality of grinding wheel segments which are attached to a lapping platen directly or through an attachment plate so that the working surfaces of the segments form one plane, wherein the surface of a material to be ground is brought into sliding contact with the grinding wheel segments to grind the surface of the material. The grinding wheel segments are arranged so that a plurality of grooves are formed extending in a direction opposite to the advancing direction of the platen from the inner side of the platen toward the outer side thereof and communicate with the outer side of the platen.

Abstract: This invention pertains to a composite whetstone for polishing soft metal plates, such as an aluminium disc, etc., which comprises matrix and fine abrasive particle. The matrix, uniform in structure, is composed of a polyvinyl acetal-based polymer, a hardened product of at least one kind of thermosetting plastic and amorphous silicate, the fine abrasive particle is incorporated into the matrix fixed substantially in close contact with each other in a continuous manner, wherein the superficial hardness (H) of the composite whetstone, measured by a Rockwell hardness tester with a superficial 15-Y scale, and the size (G) of the fine abrasive particle, determined by a classification procedure according to Japanese Industrial Standard (JIS) R-6001, have to satisfy the following relation.-180.ltoreq.H+G/55.ltoreq.-50.