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In order for the external thread and internal thread to fit together, the following must be met:
・ internal thread is greater than external thread
・ There is a gap between ★ external thread and internal thread
Now, when the external thread and internal thread are fitted, there is a gap between the ★ top of the mountain and the valley floor, and the shape does not interfere.
The part where external thread and internal thread fit together is the slope (flank) of each other's threads. In this flank surface, there is a part that represents the diameter called "effective diameter".
The effective diameter is the diameter of an imaginary cylinder in which the width of the thread is equal to the width of the thread.
The correct functioning of the screw is controlled by the thread precision, and the accuracy of the screw is
It is determined by the "effective diameter" in the flank where the external thread and internal thread come into contact.
In other words, it is managed by the gap between the flank part of the external thread and internal thread (= the difference in ★ effective diameter). Therefore, the "effective diameter" is important in screws.
There is a gap between ★ external thread and internal thread
A: internal thread effective diameter B: external thread effective diameter C: Frank Orange: internal thread Grey: external thread
★ There is a gap between the ★ top of the mountain and the valley floor
★ Frank also ★ has a gap
★ Whether the screw functions correctly (accuracy) is determined by the effective diameter.