| 摘要 |
PROBLEM TO BE SOLVED: To reduce a grinding cost of a piston ring maker, especially reduce a rough grinding cost, simplify heat remedy, contract a difference between heights of two belts of outer peripheral rail parts of a ring molding, and make each angle part sharply by setting and a difference between heights of outer peripheral rail parts and the sharp angle of each angle part to be a specified value and less. SOLUTION: Two outer peripheral rail parts are penetrated in one coil substantially, and has a good symmetric property of a cross section whose the differenceδbetween heights from a below referential surface is 0.010 and less and the difference between height sharpness of the inner sides of two belts of rail parts is 0.03 and less. The referential surface is either one of, (1) the flat surface part of a groove bottom between the outer peripheral rail parts, (2) the flat surface part of the groove bottom between two belts of inner circumferential rail parts in which there are two belts of inner circumferential rail parts on an opposite outer peripheral rail part, and (3) the flat surface for connecting the top parts of a pair of inner circumferential rail parts in which the ratio between the root widths of each length is smaller than that of the outer peripheral rail parts in the inner circumferential rail part. It is thus possible to reduce an all grinding amount in a ring maker, and simplify heat remedy. Or it is possible to improve the accuracy of a finished shape.
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