Grade markings on British Whitworth Fasteners

[EinsteinsDad]

I'm tring to identify the hardness/grade of new and old Whitworth BSF nuts and bolts. I'd like to use the equivilent of grade 8 fasteners on the suspention as I restore my 53' MGTD. Most of the old and new bolt heads I have are marked with an "R" on the head. I believe this indicates the approximate equivilant of SAE grade 5. Can anyone please give me more information about makings, hardness, coatings etc., of British Whitworth fasteners.

Thanks

 

[Britishtools]

I found this interesting article regarding this topic.
Quote:
"For British bolts the grade for high tensile is the letter "R" (45 Tons per sq in), and for American it is the letter "S" (50 Tons per sq in). The latter two equate in strength to 8.8 grade in metric."

 

[Britishtools]

I have also requested some GOOD info from our suppliers in the UK and I will post it as soon as I can!!

 

[Britishtools]

All BSF or BSW hardware is graded 700-850, which is a Grade "R"
Min - Max Hardness Brinell is 201-255

All UNC or UNF hardware is graded 775-925, which is a grade "S"
Min - Max Hardness Brinell is 223-277

Apperently there are no deviations from this grading for BSF or BSW hardware. This measurements equate a grade 8 in metric.

 

[martx-5]

According to this, metric 8.8 is equivalent to SAE grade 5.