某零件如图1所示,需要准确地测量90°锥孔的大端直径φ2.3±0.05mm。如果用直接测量法,深10mm的φ7mm孔使φ2.3±0.05mm尺寸很难直接测量,而且锥孔大径轮廓线不明显,也使之无法测量准确,必须采用间接测量法。在《航空工业检验员手册》上有一种测量锥孔大径的方法,如图2所示。已知球半径r,H_1及锥角2a,那么锥孔大径 A part shown in Figure 1, you need to accurately measure the 90 ° cone large diameter φ2.3 ± 0.05mm. If the direct measurement method, the depth of 10mm φ7mm hole φ2.3 ± 0.05mm size is difficult to measure directly, and the tapered hole diameter outline is not obvious, so that it can not measure accurately, you must use indirect measurement. In the “Aviation Industry Inspector Manual” there is a way to measure the large diameter taper, as shown in Figure 2. Known ball radius r, H_1 and taper angle 2a, then the taper hole diameter