Bolts 101

What do those slashes and numbers generally mean on a hex bolt?
It’s very simple, on clear zinc plated bolts you will notice 3 hash markings on the head this represents grade 5 which carries a tensile strength of 120,000 psi.

A gold color zinc plated bolt has 6 hash markings on the head this represents grade 8 which carry a tensile strength of 150,000 psi.

Is their a stronger bolt than grade eight?
Yes, the brand F-911 makes hex bolts and 12 point flange bolts that are rated between 180,000 & 190,000 psi tensile strength.

Harley Davidson’s have many metric fasteners. You might notice the markings 8.8, 10.9 or 12.9 this does not mean grade 8,10 or 12.
• 8.8 refers to the tensile strength which is 116,000 PSI
• 10.9 is generally 150,000 PSI
• 12.9 is generally 175,000 PSI

Now what about stainless steel bolts?
Well 18-8 stainless is great for corrosion resistance and polishes up to a brilliant finish but is not extremely strong. Most of the stainless fasteners are 18-8 and carry a 100,000 tensile strength.

Do they make a stronger tensile strength in stainless?
Yes, the brand ARP (Automotive Racing Products) offers stainless fasteners rated at 170,000 PSI tensile strength.