Thread definitions (Root Dia, Core Dia, Min Minor Dia)
Thread definitions (Root Dia, Core Dia, Min Minor Dia)
(OP)
Can anyone please give a proper definition of these three diameters on an external/bolt thread? How many are equivalent? What is a good reference for these sorts of things?
Thanks.
Thanks.





RE: Thread definitions (Root Dia, Core Dia, Min Minor Dia)
Root, Core, Minor, Major... they can all be used as reference dimensions, depending on what you are trying to do. If you want clearance holes, use Root. If you are looking to pre-dill a tapped hole, then look at Minor, ect.
"Happy the Hare at morning for she is ignorant to the Hunter's waking thoughts."
RE: Thread definitions (Root Dia, Core Dia, Min Minor Dia)
> Can anyone please give a proper definition of these
> three diameters on an external/bolt thread?
For metric or imperial bolts? And for which thread profile, if you know it or if the question is for a specific thread profile? Some possible choices for thread profile are M, MJ, UN, and UNJ, with perhaps M being the most typical. Also, do you prefer numeric formula definitions or a word definition?
RE: Thread definitions (Root Dia, Core Dia, Min Minor Dia)
"Minor diameter," with no modifier, means "nominal minor diameter." "Nominal" means "the commonly agreed-upon name of a size" or "in name only but not necessarily in actuality," and can sometimes simultaneously mean "approximate" or "approximate average."
ASME B1.13M-1995, ASME B1.1-1989, ASME B1.7M, etc., are very confusing (which implies poorly written, so even though they are a USA standard, I can't recommend them as a "good" reference), and I could not find an exact formula for "minimum minor diameter" for external threads. "Minimum minor diameter" would equal nominal minor diameter minus some thread tolerance based on the thread tolerance class of the particular thread profile, with thread tolerance class "6g" being typical for M bolts, e.g. I must defer to some thread expert who could clarify the exact "minimum minor diameter" formula, for, say, the ISO "M" thread profile with thread tolerance class 6g. Good luck.
RE: Thread definitions (Root Dia, Core Dia, Min Minor Dia)
Dm = Dn - 1.226869p for M bolts.
Dm = Dn - 1.299038p for UN and UNR bolts.
RE: Thread definitions (Root Dia, Core Dia, Min Minor Dia)