Thread template：

 With a determined pitch and tooth shape, and meeting certain accuracy requirements, it is used as a thread standard to measure similar threads. 

 Technical requirements：

 1. The surface of the threaded template should not have defects that affect the performance of the thread. 

 2. The connection between the threaded model and the protection plate should ensure that the model can be easily replaced, and the model should be able to rotate smoothly around the screw or rivet shaft, and there should be no stagnation or loosening. 

 3. The complete set of thread templates should be arranged in the order of pitch size series from small to large. 

 4. The thread model should be made of No. 45 cold-rolled strip steel or high-quality carbon steel. 

 5. The hardness of the measuring surface of the thread model should not be lower than 230HV. 

 6. The Ra value of the surface roughness of the thread sample measurement surface is 1.6µm. 

 Precautions：

 1. When measuring the pitch of the thread, use the toothed steel sheet in the thread model group as the model and get stuck on the threaded workpiece under test. If it does not fit tightly, change another piece until it fits tightly. At this time, the size marked on the thread model is the pitch of the threaded workpiece under test. However, it must be noted that when the thread model is stuck on the thread profile, the length of the thread working part should be used as much as possible to make the measurement result more correct. 

 2. When measuring the tooth angle, put the thread model with the same pitch as the thread workpiece under test on the thread under test, and then check the contact between the two. If there is no gap to transmit light, the tooth angle of the thread under test is correct. If there is an uneven gap in the light transmission phenomenon, it means that the tooth shape of the thread under test is inaccurate. However, this measurement method is very rough, and it can only judge the general situation of the tooth shape angle error, and the value of the tooth shape angle error cannot be determined. 

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