普通螺纹钻底孔用钻头直径尺寸 计算公式：P>1mm时，D=d-P； P<1mm时，D=d-(1～1.1)P 式中：P—螺距（mm） D—攻螺纹前钻头直径（mm） d—螺纹公称直径（mm）公称直径d1粗细粗细粗细粗细粗细粗细粗8细粗10螺 距P0.250.20.40.250.50.350.70.50.80.510.751.2510.751.51.25细10.75粗121.751.5细1.251钻头直径D0.750.81.61.752.52.653.33.54.24.555.26.777.28.58.799.210.210.510.71124粗22粗20粗1816粗细粗14公称直径d粗螺 距P21.5细1.25121.512.52细1.512.52细1.512.52细10.5132细1.5123456公称直径粗27螺 距32细1.51粗3.53钻头直径23.924.925.52626.326.927.928.52929.329.930.931.531.832.933.934.534.835.936.937.5公称直径粗螺 距4.5442细321.5粗4.5430细21.5145细321.5粗333.53粗54细21.548粗33细321.5细21.5粗54粗394352细321.5细21.5
