Any ratios conventions on how Bolts are partially threaded vs shank left as is? Naming/ numbering/ notations to recognize offline/ find them online?

E.g. Looking to see if there commonly exists M6 - 18 /20 mm length 8/10mm threaded, rest 10mm shank?

PS: Nice guides, but no info on how the 2 aspects (thread vs not) get set up.



  • 2
    This is interesting information in itselt, but why do you think you need it? If it's in relation to your current desk project it's irrelevant I assure you.
    – Graphus
    Oct 26, 2021 at 22:32
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    @AlexS industries are a collection of ad hoc and competing official standards. Most of us don't care about that nomenclature if we aren't in the business of supplying or using some specific fastener in a commercial setting where it might really matter. It changes with use, as well. A thing you know as a specific bolt here will have a completely different name when supplied and used on military equipment. It is also domain specific; the transport truck biz has some specific standards they require that may not be share with other domains.
    – user5572
    Oct 27, 2021 at 13:09
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    @AlexS at the end of the day, if you are a factory owner setting up some tooling, you negotiate with a fastener manufacturer to make what you want at the specs you need. The rest of us just get to choose from a rainbow of standard issue and left-overs from those factories jobs. There may be one or more standards for describing how much unthreaded shank is needed for some application where an engineer has determine they need the strength and to fit just right in a widget. Those of us in the home shop would just describe it as a length & search for the closest. Or you make your own, if possible.
    – user5572
    Oct 27, 2021 at 13:15
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    "Standards are great; everyone should have one."
    – user5572
    Oct 27, 2021 at 13:16
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    @jdv there is an xkcd for everything!
    – FreeMan
    Oct 27, 2021 at 16:22

1 Answer 1


To sum up the long discussion in comments:

As you've discovered in your searching, there is no standard naming convention for the amount of unthreaded portion of a screw or bolt. There is probably no standard amount of unthreaded portion between manufacturers, and likely not standard within a single manufacturer when comparing screws to bolts and different styles of bolts.

Unless you're an engineer designing and ordering a very large quantity of bolts that need to meet specific requirements for the assembly of a specific item, you simply buy a screw or bolt that meets your requirement of length, diameter, and pitch (particularly for machine screws or bolts/nuts). If it happens to have an unthreaded portion, it does, if it doesn't, it doesn't.

And, as always, there's an XKCD for everything:

XKCD #927 - standards proliferation

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