| 摘要 |
PURPOSE:To make radius finishing and surface hardening for each thread ridge performable so easily with a specified standard, by exposing an incomplete thread alone and, after spraying a grinding coolant it from a nozzle by dint of compressed air, spraying particulate steel balls likewise. CONSTITUTION:A thread rolling die 1 is attached to a rotary shaft 11, while complete threads 4, excluding incomplete threads 3, and side surfaces are covered with a protective member 12 of a metallic plate, a ceramic plate, etc., and then when a grinding coolant is sprayed to these incomplete threads 3 for a given period of time from a nozzle 13 by dint of compressed air out of a compressor, a pointed crest part is ground by the coolant, rounding off the angles, that is, putting a radius on each of them, whereby a surface is hardened and strength in fatigue and abrasion resistance are increased. And, furtheremore if particulate steel balls ar sprayed to these threads 3 from a nozzle similar to the said nozzle 13 by dint of the compressed air likewise, the surface of these incomplete threads 3 is still more hardened owing to hammering action by means of these steel balls.
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