To provide a rolling flat die that can suppress peeling and stripping caused in the tooth form of a base material to be roll-formed by reducing influence of circumferential speed difference between the valley and the peak of the material in a roll forming process.
A machining tooth 3 is composed of two parts comprising a rough surface part 3a formed on the tooth tip and a smooth surface part 3b formed on the dedendum. The rough surface part 3a is processed by shot blasting, with the surface roughened, while the smooth surface part 3b is applied with grinding using a grindstone, with the surface fully smoothed compared with the rough surface part 3a. Accordingly, the influence due to the circumferential speed difference between the valley and the peak of a worm tooth can be mitigated through nonslip effect by the rough surface part 3a and sliding effect by the smooth surface part 3b. As a result, peeling and stripping caused in the peak of the worm tooth can be suppressed.
UMEBAYASHI YOSHIHIRO
NAKAMURA KATSUHIRO
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