How to calculate the pitch of screw

Subtract the bit diameter from the outside diameter of the screw. For example, if the bit used for M8 is 6.75 or 6.8, then its pitch is 8-6.75 or 6.8, and the pitch is 1.25. Everything else is the same.

It is difficult to see the difference between English screws and American screws by visual inspection. The difference between English screws and American screws is that the angle of rubbing teeth is 55 degrees, while American screws are 60 degrees. These two standard screws can be used in most cases, but the screw with 1/2 specification is not, because the standard thread of English screw 1/2 is 1/2-.

Extended data:

When thread accuracy is required, besides thread code, thread tolerance zone code and thread tightening length should also be marked.

The marking format of thread mark is: thread code+thread tolerance zone code (middle diameter and top diameter)+thread length.

Except for the pipe thread, the marking method of thread mark on the view is the same as that of linear dimension. Pipe thread is in the form of guide line, which should be led out from the large diameter and should not be parallel to the section line.

The pipe thread mark shall be marked with the thread symbol and the nominal diameter of the pipe in inches. The tolerance of external thread of thread-free sealed cylindrical pipe can be divided into two grades: Grade A and Grade B, Grade A is precision grade and Grade B is rough grade. There is only one tolerance zone for internal thread, so the tolerance grade of internal thread and the right-hand direction are not marked in the label.

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Baidu Encyclopedia-Thread Marking