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.
I broke one of the bolts attaching my caliper bracket to the wheel assembly on my car. Because brakes are perhaps the most critical application in the car, I am very eager to replace it with a bolt of the correct strength grade. I am very familiar with standards in the industrial setting, but this particular bolt is perplexing me. The head is slightly recessed in the center (concave), featuring an almost centered 6 above a single dot, or perhaps a 9 beneath a single dot. I would normally buy an OEM replacement, but unfortunately it seems they are not offered by the dealer even, and I have had no luck with auto parts shops. Any insight you can provide is most welcome!
@Kevin- Our only guess is that it might be a grade 9, which is used in many OEM and automotive applications. We do not sell such items, but most auto parts stores would likely have them.
A very heavy duty, large industrial bolt fell out of nowhere and landed on the roof of my car while driving down the interstate. It caused damage and pierced into the interior of my car so I had to get a whole new roof installed. It has an “LE” on the head. Do you know what this type of bolt is used for or where it came from? Thank you!
@Carol- We are sorry to hear about your accident. “LE” bolts are manufactured by Lake Erie Products. They make many grades and types of bolts, so it is hard to determine what type that is without more information and/or a photo.
I have a question for a bolt expert, we have a bolt here that is a 1/2″x7″ galvanized square headed bolt with a T stamped in the head, we are wondering who the manufacturer may be
Thanks, Doug
@Doug- We found several different manufacturers whose head mark was a ‘T’. We wouldn’t be able to narrow it down any more without a photo. If you’d like, you can email one to dane@portlandbolt.com and we’d be happy to look at it.
I have some M14 hex head cap screws with OF on the head. Anyone know what manufacturer this is?
@Chris – Apologies, but we looked through our list of head marks, but were unable to locate OF.
Does anyone know what manufacturer head marking is 3 dots in a triangle shape. I have an indented hex head flange screw with 10.9 stamped in the middle and 3 dots around it in a triangle shape. One at the top and two at the bottom. Any help would be appreciated. Thanks!
@Ali- We looked through our list of manufacturing identifications and were unable to find the markings you describe.