How do you read the head of a bolt to know what the grade is?

I know we should only use grade 8 for automotive, but I have not idea how to figure out if its grade 8. I went to Sears hardware and they have 8.8's and K8's and all kinds of other stuff. But what does it mean?

This question is for metric as well as standard.

Thanks,
-a

 

A web search would turn up more detailed answers...

SAE Grade 8 is high strength stuff, and it's approximate equivalent to metric is "10.9".

SAE Grade 5 is equal to about metric "8.9".

I've seen metric 12.9 and assume it's stronger than metric 10.9?

SAE grade has different head markings (i.e. tick marks); metric would usually stamp the numbers on the heads.



-Ted

 

Grade 2, 5, and 8 are all SAE (fractional) measurements. Grade 2 is no marks on the head. Grade 5 is 3 marks. Grade 8 is 6 marks.

 

Right. Grade 8.8, 10.9, 12.9, etc are metric grades.
Grade 5, Grade 8, are english grades. Grade 5 ~ Grade 8.8, Grade 8 ~ Grade 10.9.

I suggest you do a web search and/or read up on www.mcmaster.com for fasteners. Mc-Master-Carr has nice little pages on materials at the beginning of common product sections.

Dave

 

Doh, that should be "8.8"...


-Ted