How to Identify Grade 8 Bolts

What You'll Need
Wire brush

Grade 8 bolts are the strongest and most durable bolt fastener used in aerospace, military, marine and heavy construction projects. Grade 8 bolts have high PSI rating due to its carbon alloy steel composition. The pre-load strength of grade 8 bolts is greater than that compared to regular bolts and Grade 5 bolts. Here are two ways to identify Grade 8 bolts from other bolts of lower grade.

Step 1-Use a magnet

You can easily identify grade 8 bolts from other bolt grades by using a magnet. Unlike other bolts with different grades, grade 8 bolts are not made of stainless steel, which means that a grade 8 bolt will not be attracted to a magnet. Position the magnet in the pile of bolts that you want to classify. The bolts that are not attracted to the magnet are Grade 8 bolts.

Step 2-Look for Bolt Markings

If you do not have a magnet you can still identify Grade 8 bolts by brushing the head of the bolt using a wire brush and counting its radial lines. There are six radial lines on the heads of Grade 8 bolts.