| 摘要 |
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</=H+G/55</=-50.
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