Bolt Hardness & Strength Guide

[BlackEclipse]

Metric bolt hardness/strength is not measured in grades. They are measured in classes. The classes are usually stamped on the head. See the following chart:

Inch Marks Material Tensil Strength Yield Strength
Grade on Head N/mm2 psi N/mm2 psi
----- ------- ------------- ------ --------- ------ -------
2 none Steel 510 74,000 393 57,000
5 3 Steel 827 120,000 634 92,000
8 6 Alloy Steel 1030 150,000 896 130,000
SHCS none Alloy Steel 1240 180,000 965 140,000
18-8 none 302 Stainless 690 100,000 448 65,000
316 none 316 Stainless 690 100,000 448 65,000


Metric Marks Material Tensile Strength Yield Strength
Class on Head N/mm2 psi N/mm2 psi
------ ------- -------------- ------ ---------- ------ -------
8.8 8.8 Steel 800 116,000 640 93,000
10.9 10.9 Steel 1040 151,000 940 136,000
12.9 12.9 Alloy Steel 1220 177,000 1100 160,000
A2-70 A2-70 302 Stainless 700 102,000 450 65,000
A4-80 A4-80 316 Stainless 800 116,000 600 87,000


If you ever have the need to cut a bolt that is Class 10.9 then do not use a regular metal cutting blade in a saber saw. You need to use a diamond-embedded Dremel cutting disc.

Ace Hardware seems to be the only place around town that sells the Class 10.9 bolts which are more appropriate for use in the "home-made" camber kit.