How to call inch threads? | YAMAWA MFG. Co., Ltd.

【英】困ったときの知恵袋詳細

Cutting TapsRoll (Forming) Taps Standard (Screw Threads, Center Holes)

In some of our drawings, there are threads such as "1/4 UNC" and "1/2W". My colleagues call the "1/4" size "nibu", and the "1/2" size "yonbu".
They have not told me why these sizes have their special name of these threads.
Could you please explain why these sizes have this thread name in Japan?

"1/4 UNC " is a Unified threads specification and "1/2W" is a specification for Whitworth threads. The Unified threads are American standard threads and Whitworth threads are British standard threads, both threads are inch-based threads.
If we read it literally in Japanese, it would be "yonbun-no-ichi (one fourth) UNC" or "ni-bun-no-ichi (half) Whit". However, since it is difficult to say and easy to misunderstand, older generations came to say this using the length unit used in the Japanese "Shaku-kan" method. For more information, please refer to the explanation below.

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