How to measure the coaxiality between the head of the torx drive socket head cap screw and the screw axis?

Mr. Qian had ordered a torx drive socket head cap screw before, but the goods and the screw and the screw that he received were not in a coaxiality. This situation affected the assembly and use of Mr. Qian. If it is obvious, we can see with the naked eye whether the head and the stem of the inner plum head are above the same axis. However, if it is not obvious, how can it be measured?

Method 1: Place the measured torx drive socket head cap screw on the V-shaped frame specified in GB/T 1219 and rotate it (no axial movement), measure with the dial gauge specified in GB/T 1219, and measure the pointer. The maximum difference in readings is shown in Figure 1.

Method 2: Firstly measure the minimum distance between the screw busbar and the wrench face or the outer circle with a caliper specified in GB/T 1214.2 of 0.02 mm, and then measure the distance value in the opposite direction. The difference between the two is the measured value.

Note: The reference surface should not consist of both the unthreaded part and the threaded part of the torx drive socket head cap screw, and the thread end should be avoided. See Figure 2 and Figure 3.

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