How to create UNJF external threads?

【英】困ったときの知恵袋詳細

Round Dies Unified Threads Standard (Screw Threads, Center Holes)

I'm producing an aircraft part that has a 1/4-28 UNJF 3A external thread. When we produced an internal UNF thread , we were able to use a YAMAWA Unified 1/4-28 UNF GH3 HT hand tap that's used for inch threads. I have used a special threading die before for an external 1/4-28UNF 3A class of fit. Can I use the same die to produce a 1/4-28UNJF 3A external thread?

Yamawa does not recommend using the special die made for a 1/4-28UNF 3A thread to produce an aerospace UNJF type thread. The diameter and number of threads per inch on both threads are the same but the minor diameter of the UNJF thread is larger. The UNJF thread also has a larger than normal controlled root radius. You must use a die designed for a UNJF external thread as it is designed to cut a larger minor diameter and the controlled root radius of a UNJF 3A thread.

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