Is 2-3/8" diameter rod stocked, or should we stick to 1/4" increments at those sizes?

Generally speaking, bolts over 1-1/2″ in diameter should be designed in 1/4″ increments, regardless of grade. While it is possible to manufacture bolts in 1/8″ increments (i.e. 2-3/8″), there are several reasons why you would want to avoid it.

  1. Steel Availability Steel round bar used to manufacture bolts is not readily available in 1/8″ increments over 1-1/2″ diameter. This means that in order to make the bolts, a special mill rolling is required. This is often not feasible, or extremely cost-prohibitive for a small anchor bolt requirement.
  2. No Defined Thread Pitches There are no published thread pitches for these diameters. In many cases specifications include allowed thread series, so the available range of specifications that the bolts could be certified is limited.
  3. Nut and Washer Availability Nuts and Washers are difficult to obtain in these diameters. In many cases, they may not exists at all and would have to be manufactured. This is a time intensive and expensive process and might not even be possible depending on the nut manufacturer’s tooling.

In almost all cases, it is best to stick to 1/4″ increments for larger diameter bolts.

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