Grade 8 Bolts: Quick Facts
A grade 8 bolt is stronger than the more commonly used grade 5. It is made of alloy steel and has six radial lines on the top of the bolt head. Grade 8 bolts have a tensile strength of 150,000 pounds per square inch. We recommend using grade 8 nuts, flat washers and high alloy lock washers with any grade 8 bolts / hex cap screws.
Grade 8 Bolts: Strength and Durability
The factor that makes a grade 8 bolt different from a lower grade bolt is its preload strength. Higher grade materials, such as carbon alloy steel, allow for greater torque strength in the threads of the bolt. The preload, or thread tension in a fastener is higher when the type of steel being used is grade 8 in quality.
Where are Grade 8 Bolts Used?
Common uses for grade 8 bolts are for military, aerospace, or marine related mechanical applications where high stress and strong load bearing pressures are a major factor. The off road vehicle market also has a need for grade 8 bolts for the same reasons. One thing to keep in mind is that it's almost always a safe bet to go with the highest grade of bolt you can when in doubt. Manufacturers may recommend a grade 5 but it never hurts to go with higher quality materials. The worst that can happen is that you paid a little more for the peace of mind.
||Radial Bolt Markings
||Nominal Size Diameter/Inches
6 Radial Lines
||Medium Carbon Alloy Steel
||1/4" thru 1 1/2"