Portland Bolt Logo Part
Home > Technical Information > FAQs > Fastener Head Markings Decoded

Fastener Head Markings Decoded

Question: Sometimes there are lines on the bolt head. What do they mean?

Grade 5 Head Marking ExampleAnswer: The lines on the head of a bolt indicate its grade. SAE J429 (Society of Automotive Engineers) bolts have radial lines, whereas ASTM (American Society for Testing and Materials) uses a combination of letters and numbers to indicate the grade. Three radial lines will indicate an SAE grade 5 fastener, while six radial lines will indicate an SAE grade 8 fastener. These are the most common grades, but there are others. Our Fastener Identification Markings Chart has a complete list of bolt grades with accompanying head markings.

Posted by Dane McKinnon

Phone: (503) 219-6991 Email: danem@portlandbolt.com
View other posts by

The below content is submitted by readers and has not been researched or checked for accuracy. It is not endorsed in any way by Portland Bolt.

11 Responses to “Fastener Head Markings Decoded”

  1. Jess Elliott says:

    We recently received HHCS with “SJ” in addition to the normal three, grade 5 hash marks.

    What does the “SJ” mean? Is it manufacturer or a foreign source material standard?


    • Jonathan Waltner says:

      @Jess Elliott – That sounds like a manufacturer’s head stamp. For example, our grade 5 bolts look like the image above.

      The US Patent and Trademark Office has a long list of registered manufacturer head insignia. You might take a look at it and see if any of them match the markings on your bolt.

  2. david krauter says:

    It is the first time I heard about these matters. I am not really keen on these head markings. But I am glad to have known about them.

  3. michael says:

    I have a 3/8 nc bolt wilt the marking that looks like a H beam with the letters B and S on each side of it.Can any one ID it.
    Thanks Mike

    • Dane McKinnon says:

      @Michael – That doesn’t ring an immediate bell, but if you want to email in a photo, I’d be happy to see if I can find it. dane@portlandbolt.com

  4. Paul Browning says:

    I have some screws with a “Star of David” mark on the top of the head, (2 equilateral triangles superimposed). Which company makes those?

  5. Rick Corcoran says:

    Anyone know the manufacturer with the marking EMM?
    Thank you.

    • Dane McKinnon says:

      @Rick – Sorry, I looked through my headmarking information(available from the US Patent and Trademark Office) and was not able to find any reference to EMM. Apologies.

  6. Luke Cowart says:

    Hello, I’ve got a screw with a “G” stamped in the head. Do you know which manufacturer that is?

    • Dane McKinnon says:

      @Luke – It is most likely Gaffney Bolt in Illinois, but there are also a few international manufacturers that use a ‘G’, so it hard to say for certain. We’d be happy to look at a photo if you wanted to send one in.

Leave a Reply


*Please note: Your comment will not appear on the site until it has been moderated. We will approve and posts comments as soon as we are able.

Ask the Expert is powered by WordPress | Entries (RSS) | Comments (RSS).