| 摘要 |
A cutter for forming a spiral groove on a work is provided. The cutter comprises a cylindrical body provided on the outer periphery thereof with a plurality of cutting edges arranged circumferentially at equal intervals and displaced axially by a predetermined pitch. Further, each of the cutting edges is provided with a pair of additional cutting edges adjacent thereto and displaced circumferentially on both sides, respectively, so that when the work and the cutter are rotated in the same direction, a high-precision spiral groove is formed on the work. A screw-shaft machined by the cutter according to the present invention is effectively used for a carriage transfer unit of a still video floppy disk drive, allowing accurate adjustment of the portion of the carriage and accurate transfer of the carriage with respect to the disk to be performed in a simple manner and at low cost.
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