Bolt

Stainless steel bolt class 8.8 means tensile strength limit of the material properties of 800MPa and yield strength of 640MPa.
Stainless steel bolts, studs, Stud grade is divided into 10 levels: from 3.6 to 12.9. In front of the decimal number represents the limit of the tensile strength of the material 1/100, decimal represent the material yield strength to tensile strength ratio of 10 times.
Nut performance score of 7 on a scale from 4 to 12. Rough stainless steel nut the minimum guarantee bearing stress 1/100.
For unified inch screw threads, external threads there are three threads: 1 a and 2 a and 3 a-class, internal thread there are three levels: 1 b, 2B and 3 b-class, all clearance fit. Higher grade number, coupled with tighter.
Level 1, 1 a and 1 b, very loose tolerances, it is suitable for both inside and outside thread tolerance fit.
Level 2, 2 a and 2 b, are inch series mechanical stainless steel fasteners provided the most common thread tolerance class.
3, 3 a and 3 b-class, spin forming tight co-ordination, stainless steel standard parts applicable to tight tolerances, for safety critical designs.