minimum exposed thread
minimum exposed thread
(OP)
I've been told that at least 3 turns of thread should be visible at the end of a bolt to ensure that the nut will maintain full tension. Can anyone explain the mechanism behind this? I'd like to know as I need to cut some bolts short in order to weld a small nut (o.d. similar to the diameter of the original bolt) to them. A transducer will then be mounted in this smaller nut.
Will the small nut provide "support" to help keep the large nut at tension?
Thanks
Will the small nut provide "support" to help keep the large nut at tension?
Thanks





RE: minimum exposed thread
Basically you need to ensure that the first thread on the nut is engaging with a fully formed thread on the bolt. Given typical lead-ins on bolts 3 turns seems a bit much.
Theoretically there's also the stress flow, which will be somewhat affected by the amount of bolt protruding.
Cheers
Greg Locock
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RE: minimum exposed thread
-- drej --
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RE: minimum exposed thread
In addition, every pipefitters handbook I've ever seen has tables showing the number, diameter, and length of studs for various classes & sizes of flanges, when using 2H (heavy) nuts. Many people think the tables are wrong - usually showing lengths that are FAR too long, but that's because they're using Gr 5 or 8 SAE bolts, and matching nuts, which are typically NOT approved for the service. If studs & matching heavy nuts are used, the lengths on the tables work out just fine.
RE: minimum exposed thread
thread725-57019
thread404-41951
thread725-37409
Regards,
Cory
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RE: minimum exposed thread
RE: minimum exposed thread
Of course drill/tap has nothing to do with the overhang allowance, but three (3) seems to be a convenient number to remember. I have never, never seen anything in the literature on it, but recall as a Junior been instructed to allow three (3) threads overhang on the nut.
It makes for a prettier AutoCad picture, but I guess five (5) full threads works just as well, aye?
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: minimum exposed thread