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

SAE J429 Grade 5The 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.

Written December 4, 2007 by
Dane McKinnonDane McKinnon

Phone: 503.219.6991


  1. 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?


    1. @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. 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. 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

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

    1. @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.

    1. @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

Your email address will not be published. Required fields are marked *