I've been told by several hardware store employees over the years that "metric bolts are all grade 8". However, a guy at AAA Metric Supply in Denver told me this week that metric bolts with 8.8 stamped on them are equivalent to grade 5, and those with 10.9 on them are equivalent to grade 8. Can any of you corroborate this?

In any event, what strength bolt do you use for important stuff - driveshaft bolts, crossmember bolts, etc?

Mark

I was told the same thing. Oh and by the way the English use Metric and before that they us BS or Wentworth. In the USA it is called SAE

yeah, metric bolts have grades just like SAE. The figures you mentioned are correct. There is also a 12.9 bolt but I cannot find the specs on it.

Originally posted by ScaldedDog
I've been told by several hardware store employees over the years that "metric bolts are all grade 8". However, a guy at AAA Metric Supply in Denver told me this week that metric bolts with 8.8 stamped on them are equivalent to grade 5, and those with 10.9 on them are equivalent to grade 8. Can any of you corroborate this?

In any event, what strength bolt do you use for important stuff - driveshaft bolts, crossmember bolts, etc?

Here's some specs on the metric grades:

http://euler9.tripod.com/bolt-database/22.html

And here are specs on the SAE grades:

http://www.americanfastener.com/techref/grade.htm

And yes, Grade 5 is similar to 8.8 and Grade 8 is similar to 10.9. I generally use Grade 5 for most things, unless I need very high clamping forces, then Grade 8.