Is A193 Grade B7 a valid specification for anchor bolts?
While there is certainly nothing to preclude ASTM A193 B7 from being specified for anchor bolts – and Portland Bolt manufactures them quite often – the specification is not intended for anchor bolt use. ASTM F1554 Grade 105 is a specification specifically developed for anchor bolts and possesses virtually identical chemical and physical properties.
ASTM A193 is a specification that “covers alloy and stainless steel bolting material for pressure vessels, valves, flanges, and fittings for high temperature or high pressure service, or other special purpose applications.” A193 B7 is widely available and mass-produced in both heavy hex bolt and all-thread rod form, so it is a very familiar specification to engineers, contractors, fastener distributors, and bolt manufacturers. This may be one of the reasons it is so often called out for anchor bolt applications.
Another key reasons that A193 B7 is not the most suitable specification for anchor bolts is the requirement, per the A193 compliance with ASTM A962, that A193 fasteners 1″ diameter and larger shall be 8 thread pitch series (8 threads per inch), unless otherwise specified. While the “otherwise specified” language means that A193 anchor bolts can still be made with national coarse threads, the 8 TPI requirement could result in higher manufacturing costs and limited availability and higher costs on larger diameter nuts, particularly galvanized nuts. In fact, there is no standard, published oversizing allowance for 8 TPI galvanized nuts above 1-1/2″ diameter.
ASTM F1554 Grade 105 would be a more appropriate specification than A193 B7 if the application is anchor bolts. As mentioned above, F1554 is an anchor bolt specification. The chemical and mechanical properties are nearly identical. For diameters up to 2-1/2″, the minimum yield (105 ksi) and tensile (125 ksi) are exactly the same (although F1554 Grade 105 does have a maximum of 150 ksi tensile, while A193 has no maximum). Additionally, with F1554, there are no special thread pitch requirements.