There is no substantial difference between 6HX and 6H in thread accuracy, and both of them can be tested with 6H ring plug gauge. The only difference is the faucet. 6HX takes the upper deviation of 6H as its lower deviation. In German standards, the tolerance of 6H is 0- 180, the tolerance of 6H tap is 42-70, and the tolerance of 6HX is 70-98. When the processing materials are wear-resistant castings (such as cast iron, cast aluminum) and plastics, 6HX precision taps are selected according to experience. In addition, due to the design reasons of the tap itself, the design accuracy of straight groove tap and extrusion tap is usually 6HX, and the design accuracy of spiral groove tap (especially large spiral angle) and spiral tip tap is 6 h.

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