On Tapping with the Left Spiral Fluted Taps
Yoshinobu FUJII, Yoshiya Fujii · Journal of the Japan Society of Precision Engineering · 1965
This report deals principally with variation of the tapping torque by the left spiral and the straight fluted taps for the duralumin and the cast iron FC 20. As conclusions, (1) The helix angle of the left fluted taps is recommended to be 13 to 15 deg. for the duralumin because chip flow becomes smooth.(2) From the dimensional analysis, the following equation for tapping torque is derived.T=p2deks(k1+k2Vp/D)where T=tapping torque, p=pitch, ks=specific cutting force, V=cutting speed and D=thermal diffusivity. And also k1, k2 are the constants.