Bolt head "letter" identification

[tmcgett]

Looking for info on a grade 8 ( 1" shaft dia. ) with the letters "BY" on center of head. What's the BY stand for?

Also this bolt was used instead of a required grade 10.9
( 27mm / 1" 1/8 shaft dia. ) on a critical structure.

What magnitude of danger if any would this pose ?

Thanks

 

[FOETS]

If it says 8.8 on the bolt head then its an ISO bolt. The BY could be a manufacturers marking

Difference between 8.8 and 10.9 is significant

proof load (psi) 85000 vs 120000
min yield strength (psi) 92,000 vs 130000
min Tensile Strength (psi) 120000 vs 150000

The danger depends on the application, but if it calls for a 10.9 then it should be a 10.9

 

[FOETS]

http://www.boltscience.com/

check the website above for useful advice on fasteners