How do I know if the coating or plating I am stocking will meet a specific customer’s requirements?
Historically, when designers wanted to ensure that an assembly did not come loose, they would require that the bolt be “double-nutted”. Double nutting is an effective way of preventing an assembly from loosening, but it is not the most cost-effective way.
Question: Why is the hardness of a Grade 8 Nut lower than the hardness of a Grade 8 Bolt?
Grade 8 bolts have a specified hardness of Rc 33/39.
Grade 8 nuts (in diameters up to 5/8”) have a specified hardness of Rc 24/32.
A rule of thumb for fastener applications is that the strength of the nut should be equal to or stronger than the bolt. Since hardness has a direct correlation to strength, it is logical to assume that since the hardness of the nut is lower than the bolt, then the nut is not as strong.