Are heavy square head bolts and heavy square nuts available?
According to ASME, a global standards organization which provides manufacturers with guidelines and tolerances for producing parts, there are no listed dimensions to manufacture heavy square head bolts. However, ASME does provide dimensions for heavy square nuts.
This standard covers the dimensional requirements for nine product types of inch series bolts and screws recognized as American National Standard. Included in the standard are: square, hex, heavy hex, and askew head bolts and hex, heavy hex, hex flange, lobed head, and lag screws (inch series). The standard makes no mention of heavy square head bolts. For that reason, Portland Bolt would not be able to provide a heavy square head bolt since there are no given dimensions to make the parts. Custom tooling can be produced to customer-provided dimensions for a “heavy square head bolt” but the cost and lead time to have the tooling made may be prohibitive unless a larger production run is required.
This standard is intended to cover the complete general and dimensional data for various types of inch series square and hex nuts, including machine screw nuts and coupling nuts, recognized as American National Standard. While heavy square nut dimensions are given in Table 8 in ASME B.18.2.2, section 1.1.2 from B18.2.2 gives us this word of caution, “The inclusion of dimensional data in this Standard is not intended to imply that all of the products described herein are stock production sizes. Consumers are requested to consult with manufacturers concerning lists of stock production sizes.” In the case of heavy square nuts, dimensions are provided but the items are not mass produced so the availability will be scarce.