A490 Bolts?

[psychedomination]

Hi there,

Quick question. Why is a washer required under the nut and head for an A490 bolt? Is it because of the increased material hardness?

 

[DLBridge]

Generally speaking yes. The hardened washer prevents galling under the turned element. RCSC Specification for Structural Joints Using High-Strength Bolts goes into more detail about the use of washers in Section 6.

Link:

http://www.boltcouncil.org/files/2009RCSCSpecification.pdf

 

[hokie66]

That Section 6 says it all, so follow the specification rather than what we say. To clarify, in most cases, the washer is only required under the turned element. But where the bolt is a lot harder than the steel member, a washer is needed under the other side as well.