Ned Simmons wrote:
On Mon, 27 Jul 2009 20:16:21 -0500, "Karl Townsend"
wrote:


Grade 8 bolts drill nicely. In fact I will do the same today.

I hope you're right. This is a metric button head fine thread. Won't be easy
to find another. Murphy is my partner. I wouldn't even ask if i had a
practice bolt or two.


Unlike US alloy socket heads, metric socket heads come in different
grades. The most common (class 12.9) is similar to US alloy socket
heads, and perhaps 5 points harder than a grade 8 cap screw on the Rc
scale.


Also I don't think the button head mentioned are made in 12.9, I think
they are only made upto 10.9, maybe due to the smaller socket limiting
the tightening torque possible. The supplier should know.