Bolt strength
 

I have bought some seat bolts which I thought were 8.8 grade but the tops just have 3 lines on them. Does anyone know if they are the same strength. I am thinking that this is because they are imperial

Am I correct?

David

Medium carbon steel bolts.

M & S in Newburn can supply most nuts bolts rivnuts etc and cheap for cash too.

Are medium carbon steel not the same as 8.8

David

Think I've found the answer

Metric 8.8 is equivalent to a grade 5. Metric 10.9, 12.9, are equivalent to grade 8.

Tensile is 90/120,000 on those three mark ones so 8.8 is the lowest used in automotive as far as I remember for general use,10 upwards for more strength and over engineered for safety.