Standard vs. Non-Standard Structural Bolts

Sometimes, we’ll refer to a structural bolt as “standard” or “non-standard.” Basically, standard structural bolts have a body length and thread length based on ASME standards (Ref. ASME 18.2.6). Non-standard refers to bolts that are not on this chart, but can be custom made to fit customer needs. Non-standard structural bolts can have special characteristics – for example: a hex configuration instead of a heavy hex head, fully threaded structural bolts, and other non-standard features. You will not find non-standard bolts readily available on the market. Instead you will seek out a manufacturer, like Birmingham Fastener Manufacturing, to fulfill your needs.

Standard Structural Bolts

As we discussed in our blog post covering the governing bodies of structural bolts, the American Society of Mechanical Engineers (ASME) produces codes and standards for many different technical fields, including the fastener field. In regards to fasteners, the ASME provides manufacturers with dimensional standards for all types of bolts, including structural bolts. For structural bolts, these standards include everything from body diameter and head height to thread length and identification symbols.

Being most commonly ordered, standard structural bolts are generally kept in stock by most manufacturers and distributors. Because of this, there’s a faster turnaround time than non-standard structural bolts.

Non-Standard Structural Bolts

Unlike standard structural bolts, non-standard may not follow all of the standards in the ASME. You may have a special project that requires a fully threaded structural bolt. Because standard structural bolts have a shank, you will have to source a manufacturer to make these for you. Per ASTM F3125, a “T” or “S” is added onto the bolt head markings to signify a non-standard configuration. The “T” is used for fully threaded bolts. The “S” is used to signify special head configuration, thread length, or other special characteristics.

Order time does take longer for non-standard bolts, but you will be able to get exactly what you need. It’s important to find a manufacturer that is well versed in custom work. Communication is paramount when ordering non-standard structural bolts, so it’s important to go with a company you can trust.