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.
Is B18.2.1 a standard head and thread for UNC socket head cap screws? I’ve got a job that specifies ASTM S354 Grade BD material and ASME B18.2.1 “form”. That’s a new one for me.
@Steve- ASME B18.2.1 covers the standard dimensions for many headed bolts like hex, heavy hex, square, etc. It does not cover socket heads, because socket head cap screws are covered by ASME B18.3. ASTM A354 BD bolts are more commonly made to the B18.2.1 hex bolt standards, whereas socket head cap screws are typically made per ASTM A574.
Hi Mike:
Could the ASME (ANSI) B18.2.1 standard ALSO be referred to as the fastener ‘cut sheet’?
@Thomas- Most of the dimensions that we use to generate our internal cut sheets are pulled directly from that ASME standard, so from a dimensional standpoint, you could call it that. However, there are many grades of fastener that could all have those same dimensions, so if you were using only that standard for your cut sheet, it would be missing the grade and mechanical information.