直柄麻花钻除柄部外,其工作部分(刃部)的直径略有前大后小的倒锥度,其值为0.03～0.1/100 mm。为提高麻花钻无心磨削的生产效率,过去许多生产麻花钻的专业厂,对通磨法无心磨制作过不同程度的试验,但至今没有普遍推广,而仍采用切入法完成工作部分的倒锥度加工。由于切入法为间断 Straight shank twist drill in addition to the handle, the working part (blade) diameter slightly before the big after the small taper, the value of 0.03 ~ 0.1 / 100 mm. In order to improve the production efficiency of twistless centerless grinding, many past professional manufacturers of twist drills have done tests of different degrees to the grinding method of centerless grinding. However, there is no general promotion so far, Processing. Due to the cut-in method is intermittent