Hex Bolt Fastner Grade Ratings

[sbe]

I have noticed that in factory manufactured equipment i.e. UPS, the internal hex bolt fastners are grade-5, but we have been using grade-2 with either belville or standard lock washers(Acorn Fastner brand mfg.) for the field connections which is what is available at our local electrical supply. Are the grade-2 fastners acceptable? What are your thoughts?

 

[bphgravity]

Re: Hex Bolt Fastner Grade Ratings

SAE Grade 5, 1/4"-1" hex bolts have a minimum yield strength of about 92,000 psi.

SAE Grade 2. 1/4"-3/4" hex bolts have a minimum yield strength of about 57,000 psi.

The material type (low or medium carbon) and whether the bolt has been tempered or not changes the numbers a bit. Also, fine threads are stronger than course threads for tensile strength believe it or not? Proof and Tensile strengths are at the same ratios.

I prefer Grade 8 Stainless for outdoor equipment installations.

 

[sbe]

Re: Hex Bolt Fastner Grade Ratings

I agree that stainless steel is used for outdoor work, as in a utility transformer. But my concern is where are the listing requirements, or where can I find these requirements for what grade to be used.

[ April 16, 2004, 07:18 PM: Message edited by: sbe ]

 

[websparky]

Re: Hex Bolt Fastner Grade Ratings

IMO:

I think you are asking about a NEMA standard. When in doubt, use grade 5 minimum or grade 8 if the connection stress warrents it.