How to Identify a Grade 8 Bolt


Grade 8 bolts are specified for high strength applications and should not be replaced with regular bolts or bolts of a lesser hardness grade. The system used to mark the heads of bolts with simple symbols makes identifying the various grades of bolts easy to learn and remember.

Things You'll Need

  • Wire brush
  • Try to pick up the bolt with a magnet. Grade 8 bolts are not made of stainless steel and will be attracted to the magnet; stainless bolts will not be attracted to the magnet.

  • Clean the head of the bolt with a wire brush to see if any bolt markings are present.

  • Examine the head of the bolt and count the radial lines. Grade 8 bolts have six radial lines and no numbers. The absence of radial lines indicates a regular bolt; three radial lines indicates a Grade 5 bolt.

Tips & Warnings

  • Don't consider the color of the bolt when identifying bolt grades. Bolts can be plated without affecting hardness or grade.

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