Special caliper for measuring large-end diameter of taper hole of oil drill female adaptor

The utility model relates to a special caliper for measuring a large-end diameter of a taper hole of an oil drill female adaptor, which mainly comprises a main measurement ruler (1), a fixed scale (2), a vernier scale (3) and spherical contacts (6), wherein the main measurement ruler (1) is of a rectangular ruler, and length graduations are arranged on the main measurement ruler (1); graduations are arranged on the vernier scale (3), and the fixed scale (2) is fixed at one end of the main measurement ruler (1); the vernier scale (3) is arranged on the main measurement ruler (1), and the fixed scale (2) is parallel to the vernier scale (3); and the spherical contacts (6) are respectively fixed at the outer sides of the fixed scale (2) and the vernier scale (3). The utility model has the effects that the problem that the large-end diameter of the taper hole of the oil drill female adaptor can not be directly and precisely measured can be solved, and the accuracy degree and efficiency of measurement are improved.