These represent threads 3-M2-6H. For example, there are three threads on the workpiece, M2 is a flexible thread with a diameter of 2mm, 6H represents the six-level accuracy of the basic hole system, which is evenly distributed (on the straight line and circumference), and depth 6 represents depth 6(mm). G stands for pipe thread, Z stands for taper thread, and the thread profile has corresponding national standards.
Thread contour machining
For fastening threads and transmission threads without transmission accuracy, the surface machining of threads refers to the dimensional accuracy of pitch diameter and top diameter. For transmission threads with transmission stroke requirements, besides the dimensional accuracy of pitch and crest diameter, the dimensional accuracy of pitch and crest diameter is also required, but the domestic standard values stipulate the dimensional accuracy of pitch and crest diameter, which is guaranteed by the dimensional accuracy of pitch and crest diameter.