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.
Anyone know the manufacturer with the marking EMM?
Thank you.
@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.
I have some screws with a “Star of David” mark on the top of the head, (2 equilateral triangles superimposed). Which company makes those?
@Paul – I am not sure who’s marking that is, but you may be able to find it listed on the US Patent Office Fastener Insignia Register here https://www.uspto.gov/trademarks/law/FQA_Registry.pdf
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
@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
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.
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?
Regards,
Jess
@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.