内螺纹在攻丝前的底孔直径大小会影响螺纹的质量,底孔过大,不能攻出完整的螺纹;底孔过小,会造成丝锥在攻丝中折断。我们在工作中,采用如下经 The size of the bottom hole of the internal thread before tapping will affect the quality of the thread. The bottom hole is too large to be able to tap the complete thread. If the bottom hole is too small, the tap will be broken in tapping. In our work, we adopt the following