Heavy hex nuts to ASTM A194: 2H, 4, 7 and 8

Heavy hex is the heavy series of the American hex nut to ASME B18.2.2: it has a larger width across flats and a greater height than the metric nut to ISO 4032 or the lighter standard hex nut. This ensures sufficient thread engagement with high-strength bolts, so that the bolt rather than the thread is the limiting element, and it gives the wrench a larger contact area. Heavy hex nuts are used with stud bolts and heavy hex bolts on flanges, valves and pressure vessels to ASME.

Grades to ASTM A194

• 2H: Quenched and tempered carbon steel, the standard nut for B7 stud bolts for temperatures up to approximately 400 °C.
• 2HM: As 2H, with limited hardness for sour service, matching B7M.
• 4 and 7: Alloy, quenched and tempered steels for higher temperatures and for low-temperature applications; grade 7 matches B16 and L7; 7M with limited hardness.
• 8 and 8M: Austenitic stainless steels, matching B8 and B8M.
• Suffix L: Low-temperature impact testing (Charpy), for example 4L or 7L for L7 bolts.

Metric equivalents

Metric stud bolts take nuts of a property class to ISO 898-2, for example class 10 for 10.9 or class 8 for 8.8, often as style 2 (high) nuts to ISO 4033 or to DIN 2510 as nuts for reduced-shank bolts.

How RS Randack produces nuts

Hot-pierced and forged or turned from solid, hexagon milled, quenched and tempered by qualified partners, internal threads tapped or turned, typically up to M80 and correspondingly around 3 inch, proof load test and hardness in our own laboratory, marking with grade and manufacturer’s mark, coating to match the bolt, with an oversize thread where the coating requires it. Nut and bolt are supplied with a single certificate.

What you should specify

Thread and class, grade, height and width across flats to standard or drawing, coating, certificate type and whether the nuts belong to bolts from the same order.