I suppose here lies the confusion. I should have been a little more specific. i.e Grade 8.8 bolts, Class 8.8 or Grade 8. beleive it or not they have all different tensile ratings. Basic rule of thumb is that fasteners with a "grade" are imperial scale rated and fasteners with "Class" are metric scale rated. This is irrelivent of the thread and pitch.
Class 8.8 bolts are rated as
Structural High Tensile and Class 10.9 are rated at
Higher Tensile. Both are well above the everyday regular bolt [Class 4.6/ SAE Grade 2]. Unfortunately its abit like comparing apples and oranges, they are both fruit, but thats about it in the similarities.
Metric to Imperial table would be something like this:
Metric Class 4.6 [mild steel] --- SAE Imperial Grade 2 [mild steel]
Metric Class 8.8 {High Tensile] ---SAE Imperial Grade 5
Metric Class 10.9 [Higher Tensile] --- SAE Imperial Grade 8
This is only a rough guide because the metric tensile load rating is slighly higher than the Imperilal tensile load rating when comparing the two figures.
see chart for source information.
bolt tensile ratings
Transfer
