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Thread gage marking 2A and 2B

Thread gage marking 2A and 2B

Thread gage marking 2A and 2B

(OP)
Hi All

A simple question, would like to know your comments before I contact with the gage maker.

For the thread gage 1/4-28 UNF-2B, I know 2B means internal fit, 2A means external fit, I can not realize why 2A and 2B marked on the same gage, please ref to the attached for details.

Thanks for your inputs

Season

RE: Thread gage marking 2A and 2B

It's a plug gage. For use in checking an internal thread presumably. As you already know, an internal thread is designated by "B".

Typically a double-ended gage like that would have a "GO" and a "NO-GO" end (with the NO-GO end often colored red.

So to me it looks like a typo - but on the gage itself. The packaging appears correct.

RE: Thread gage marking 2A and 2B

The -2B marking on the gauge may mean that the gauge is intended to be used to inspect an internal thread.

Tunalover

RE: Thread gage marking 2A and 2B

It should be fairly obvious that an externally threaded go-no go gauge is intended to be used for checking internal threads. Otherwise how would you use a gauge with external threads to inspect parts also having external threads? The C-of-C provided with the gauge only states that the gauge has been inspected in accordance with applicable standards. And the markings on the gauge clearly indicate it is intended for inspecting a 1/4-28 UNF-2B thread. So you have no reason to gripe with the vendor except to ask for a suitable replacement gauge, which I'm sure they will be happy to provide.

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