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STUD Bolt ASME standard

STUD Bolt ASME standard

RE: STUD Bolt ASME standard

This has always been a kind of strange thing (to me). The standard for studs, afaik, is B16.5. Now, B16.5 doesnt really specify studs as youd expect from an ASME standard. B16.5 also doesnt reference B18.31.2. Simply looking at B18.31.2 without checking details for compliance on B16.5 studs, it details fully threaded studs in more detail than B16.5 does, however B18.31.2 doesnt reference B16.5 at it's turn.
So if your questions is 'Should studs for B16.5 flanges be acc B18.31.2", I guess the answer is no.

RE: STUD Bolt ASME standard

In addition to XL83NL's comments, a stud bolt (B16.5) is not the same as continuously threaded stud (B18.31.2) per the definitions in B18.12.

There's truly not much difference between a B16.5 stud bolt or a B18.31.2 continuously threaded stud. Through talking with bolt experts and companies I've found out that the B16.5 term "stud bolt" has sort of been grandfathered-in. A stud bolt per the B18.12 definition is permanently screwed in on one side with a nut on the other. While a continuously threaded stud is typically used for flanged applications. B16.5's purpose of supplying stud bolt lengths is to provide the engineer or designer with a stud that has a length to which both nuts on each side of the flange are fully engaged (a B31.1 requirement). However, in todays age it is becoming more popular for utlities,contractors,design firms, etc. to specify that 1-3 threads be exposed past the nut (purely for quicker visual examination to make sure that B31.1 requirement for full engagement is met). That being said, if you use a B16.5 "stud bolt" length you likely will not achieve 2 or 3 exposed threads beyond the nut. This is when you would go to B18.31.2 for guidance on what length you would need.

The foreword of B18.31.2 is helpful in understanding the history of a "stud bolt" and a "continuously threaded stud".

To answer your question, if you just want a standard bolt use the lengths in B16.5. If you have a requirement for extra exposed threads I would use B18.31.2 as a basis in determining your length.

P.S. The main differences that Ive noticed between B16.5 "stud bolts" and B18.31.2 "continuously threaded studs" are the chamfer tolerances and overall length tolerances. Also, a stud bolt is measured first thread to first thread while a continuously threaded stud is measured end to end typically.

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