What grade of coupling nut should I use?


A common question that we encounter has to do with what type of coupling nut should be used in conjunction with a particular grade of bolt or rod. Typically, a coupling nut would be specified as a grade of nut, as opposed to a grade of bolt. The ASTM grade of hex nut that is compatible with a particular grade of bolt or rod would typically be specified. For instance, per the F1554 specification, A194-2H or A563-DH heavy hex nuts are the recommended nuts to be used in conjunction with F1554-GR105 bolts or rods. Therefore, if you are coupling two F1554-GR105 rods together, the coupling nut would normally be called out as either A194-2H or A563-DH.

A typical, standard coupling nut length is three times the bolt or rod diameter. Some coupling nuts that are mass-produced are slightly shorter however. Longer coupling nuts can be manufactured as well.

Portland Bolt does not employ any engineers, so the frequent question of whether or not the coupling nut will “develop the strength of the rods,” should be directed toward an engineer.

For reference, see our table on coupling nut dimensions or our nut compatibility chart

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