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Thread: ANSI/ASME Standards for Fasteners - Thread Length Inquiry

  1. #1
    Associate Engineer
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    ANSI/ASME Standards for Fasteners - Thread Length Inquiry

    Hello all,

    I do not have the actual ANSI/ASME standards for the fasteners I am looking into, however, I am able to get dimensional info and some ANSI standard information using the Machinery's Handbook (26th edition).

    From my understanding, if one were to order a Hex bolt (for example) that coincides with the ANSI/ASME B18.2.3.5 standard, then that person would receive a bolt with a partial thread of length "X".

    If I am interested in a FULLY THREADED hex bolt, would it still fall under that standard?

    In other words, do the ANSI standards for hardware specifically target certain thread lengths? A vendor has stated that they do; however, if I were to use a hex bolt in the Solidworks Toolbox, it gives me the option of selecting a full thread and still describes the bolt as being a ANSI standard piece of hardware.

    I hope this makes sense.

    Thanks for taking the time to address this.

  2. #2
    Administrator Kelly Bramble's Avatar
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    Welcome to Engineers Edge Forum!

    I don’t know if the standards you mention control standard thread lengths..

    The un-threaded portion of a bolt is referred to as the "Grip" and should be the portion of the bolt that that is against any shear or load interface or surface.

    Keep in mind that it is very difficult to actually thread (manufacture) a bolt all the way to the head. Terminating the thread against a surface that is perpendicular to the thread is almost impossible if not expensive. So, the last thread or “scratch” is usually worthless. Standard thread design should allow around 1.5 x pitch, but not less than .050” between the last scratch and the perpendicular bolt head surface.

    A way to actually terminate a thread relative to a surface perpendicular is to use “All-Thread” or a threaded rod with a nut and washer if required. A stud and nut works as well.
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