What is ANSI B18.2.1?

Often times, ANSI (American National Standards Institute) or ASME (American Society of Mechanical Engineers)  B18.2.1 will show up on a drawing, some certification documents, and even our website . This number simply refers to dimensional standards for a variety of common bolts, such as hex bolts, heavy hex head bolts, and square head bolts. Most ASTM specifications do not address dimensional tolerances of fasteners.  Instead, most ASTM bolt specifications refer to an ASME standard for this information.  Bolt manufacturers must comply with ASME standards for dimensions such as head height, width across the flats, body diameter, bolt length tolerances, thread lengths, and dimensional tolerances in general.  ASME B18.2.1 does not have any bearing on the strength or the chemistry of the bolt, which is typically called out by an ASTM or SAE grade designation.

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4 comments

    Mike,

    Would you know the yield strength of a ASME B.18.2.1 bolt of the following size: 1.5 X 6 UNC ?

    Thank you,
    Carlos Muller
    General Dynamics Mission Systems

    @Carlos- ASME B18.2.1 only covers the dimensions of the bolt, not the steel type or mechanical properties. If you know the grade, we can help determine the minimum yield strength.

    Hi Mike,

    I hope you can help me. We need to attached a inside metal railing (200lbs) to a wooden beam (14×5) – we have 10 attachment points. The railing contractor suggested using 3/8 x 2 1/2 wooden lag bolts but mentioned that he wanted to make sure we don’t rip of the heads using an impact wrench. Also what time of head and coating would you recommend.

    Regards
    Albrecht Gass

    @Albrecht Gass- I would be careful using an impact wrench when installing 3/8″ lag bolts, as the heads would likely shear off with a powerful wrench like that. As for head style and coating, a hex head will be the most common head style of lag bolt. Outdoor applications normally require a hot dip galvanized coating, whereas for indoor applications, plain finish or electro zinc coated is probably sufficient.

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