ASTM A194 Grade 2H Heavy Hex Nuts

ASTM A194 Grade 2H nuts, also called A194 2H nuts or 2H heavy hex nuts, are quenched and tempered medium-carbon steel nuts specified for high-pressure or high-temperature bolting service. The 2H grade is commonly supplied in the heavy hex form, with a larger wrenching profile and greater thickness than a standard finished hex nut.

These nuts are commonly used with high-strength studs and bolts such as ASTM A193 Grade B7 in flange connections, piping systems, pressure vessels, valves, and petrochemical or power-generation equipment. The nut’s dimensional form is governed separately from the A194 material specification; ASME B18.2.2 covers inch-series hex nuts, while ASME B18.2.4.6M covers metric heavy hex nuts.

For inch-series configurations, UNC threads are commonly used on smaller nominal sizes, while 8UN is commonly used from 1 inch and above. Metric sizes are covered within the A194 size range as well. Plain and hot-dip galvanized versions are commonly supplied, with coated nuts requiring appropriate thread and coating considerations.