To measure the hex bolt, measure it with a caliper. The method of measurement is generally to measure the thread diameter and thread length. If it is a half thread, in addition to measuring the thread length, the diameter of the metering rod and the total length of the polished rod and the thread are measured. The diameter of the polished rod, and then the diameter of the thread, can be determined that the screw needs to be processed by the shrink rod; after the thread is measured, the tooth distance can be measured, and then the head is measured.
If it is a hexagonal head, the hexagonal edge needs to be measured. The diagonal can be measured, because the across of flat can calculate the diagonal, and then measure the thickness of the hexagon. If it is a hexagon socket, not only the hexagonal side, but also the hexagonal depth, then the head diameter and the thickness of the head.