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Bolt grade marking F8 325
2

Bolt grade marking F8 325

Bolt grade marking F8 325

(OP)
I am evaluating a structure some ~50 years old and don't have general notes so I'm checking bolt strength by look at the grade stamped on the head. I have three lines indicating medium carbon steel, but then the grade is F8 325. Am I correct in calling this A325? Photo attached. Hopefully a stupid question...

RE: Bolt grade marking F8 325

Your assumption is reasonable. The F8 is a mystery though. It doesn't appear in the current A325 spec. Monday when I get back to the office I'm going to see if the ancient ASTM spec is available.

Could F8 be FB; possibly a manufacturer? Attached is a fastener identification guide from Illinois DOT - it's the most extensive guide I've ever come across - anyway there's no F8 or FB listed.

RE: Bolt grade marking F8 325

I think you are very safe assuming the bolt is ASTM A325 material. Looking through the ASTM A325 Specifications included with the 6th and 7th edition AISC Steel Construction Manuals, I don't see any specific mention of "F8" but it could very well be a manufacturer's mark (as bridgebuster mentioned).

RE: Bolt grade marking F8 325

The oldest A 325 spec I have is from 1984 but no reference to "F8".

RE: Bolt grade marking F8 325

Could the 'F8' be 'PB' for Portland Bolt? They've been around a long time.

RE: Bolt grade marking F8 325

(OP)
Looking into, I would say it's almost certainly meant to be PB. Thanks

RE: Bolt grade marking F8 325

Two indispensable tools for this sort of work are a small stainless steel brush, about the size of a toothbrush, and a 10x Loupe (or as the old timers used to call them, an Aha......meaning, "Aha, so that's what that is!")lol

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