A Quick Guide to Fastener Identification

Whether you’ve been a Kimball Midwest customer for years or you are considering making the switch from your previous supplier, chances are you know the frustrations of disorganized fasteners.

As a smaller item in your shop, it’s easy to see why they so often get lost or put out of place. We understand this headache, which is why we want to make sure you know how to properly grade your fasteners so you aren’t left with a bunch of mismatched fasteners in a pile when the time comes to clean a workspace.

Here is a small cheat sheet to reference when you need to identify cap screws and their corresponding hex nuts.

Cap Screw ID – Grade Specifications

• Grade 2
  • No markings
  • Minimum tensile strength: 60,000 psi
  • Corresponding hex screw has no markings.
  • *Not sold by Kimball Midwest
• Grade 5
  • Three radial lines spaced 120 degrees apart.
  • Minimum Tensile Strength: 120,000 psi
  • Corresponding hex screw has three radial lines spaced 120 degrees apart or a dot and a line (or two lines) 120 degrees counterclockwise from the dot.
• Grade 8
  • Six radial lines spaced 60 degrees apart.
  • Minimum tensile strength: 150,000 psi
  • Corresponding hex nut has six radial lines spaced 60 degrees apart or a dot and a line 60 degrees (or two lines) counterclockwise from the dot.
• L9
  • Nine radial lines spaced 40 degrees apart.
  • Minimum tensile strength: 180,000-200,000 psi
  • Corresponding hex nut has nine radial lines spaced 40 degrees apart.

Cap Screw ID – Metric Specifications

• 8.8 Metric is equivalent to Grade 5 fasteners and can be identified with an 8.8 on the head.
  • The corresponding hex nut is identified by a I8I marking.
• 10.9 Metric is equivalent to Grade 8 fasteners and can be identified with a 10.9 on the head.
  • The corresponding hex nut is identified by a 10 marking.

Cap Screw ID – Stainless Steel

• 316 Stainless
  • Identified with ASTM spec F593G, F593H or 316 on head. The corresponding hex nut and washer is identified with a 316 marking.
• 18-8 / 304 Stainless
  • Identified with ASTM spec F593C or F593D on head. The corresponding hex nut and washer do not have any identifying marks.

In addition to cap screws and hex nuts, lock nuts and washers are commonly misplaced fasteners, as well. While we could write a whole blog just for identifying those, our sales reps are able to help you identify these or if you have any other fastener questions.

If you need help identifying, organizing or need to stock up on your fasteners, contact your Kimball Midwest sales representative today. If you do not have a sales rep, we can help you