What is the effective diameter of a screw?
It is not easy to obtain a specified dimension in thread processing.
A thread has elements such as the outer diameter, inner diameter, root diameter, distance between adjacent threads (pitch), thread angle, and effective diameter.
Among these elements that determine the shape of a thread, the "effective diameter" and its tolerance are important.
"Effective diameter" is the diameter of an imaginary cylinder (or cone) where the width of the thread groove is equal to the width of the thread.
When looking at the standard thread shape, there is a gap between the crest of the male thread and the root diameter of the female thread, and also between the root diameter of the male thread and the inner diameter
of the female thread. The "diagonal part" of the thread (called the flank surface) is important in determining whether the thread is tight or loose.
The concept of "effective diameter" exists to control this flank surface.
A general thread gauge inspects this "effective diameter".
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