タップの切削トルクの解析 (第1報)

Abstract

The discussions in the previous report are limited to a special case such as a plug tap, in which chamfer angle α is so small that its effect can be neglected. When the angle is increased, however, it is necessary to consider the effect of the angle on tapping as in the case of bottoming tap. Taking the above effect into account together with the variation of the specific cutting resistance K (γ), that was clarified in the previous report, the torque of tapping is theoretically and experimentally analyzed in this report. The results obtained are as follows : (1) Distribution of the specific cutting resistance K (γ) acting at every edge in the chamfer of a bottoming tap can be expressed in the following simple form. K (γ) =K0 cosh α (γ-s) where, γ : distance of cutting edge from tap axis, K0, α, s : const. As an example, by a bottoming tap (M8 × 1.25) K (γ) =270 cosh 5 (γ-3.60) kg/mm2 (S35C Steel, Hardness : HRB 87) As another, by the same tap K (γ) =85 cosh 5 (γ-3.58) kg/mm2 (BSBM2 Brass, Hardness : HRB61) (2) Function K (γ) is experimentally obtained by the conventional fluting in which cutting conditions are determined by the tap used above and its tapping conditions. (3) K (γ) enables us to calculate the theoretical tapping torque which coincides exactly with the torque measured by experiments.