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.

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    Hello, I have a hex bolt with the markings SB on one end of the bolt head and then R on the opposite end of the bolt head. I’m trying to find the manufacturer or a location to buy more but the local hardware stores I’ve visited say the bolt is not US or metric standard. Would you happen to know what those letters represent? Thank you.

    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.

    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.

    The local Tractor Supply sells a 1/2″x3″ hex head bolt (19mm) that has HFG stamped in the center and an unusual stamp below it, more like a symbol than letter. No radial lines. Is this a grade 2 bolt? Store employees do not seem to know.

    @Stuart- Our guess is that your bolt is an SAE grade 2 bolt. Most other SAE and ASTM grades require grade marking, so in the absence of that, grade 2 seems like the most likely grade. As for the HFS and symbol, that is more than likely the manufacturer’s stamp. I’d assume the symbol is part of that.

    If it is a bolt from tractor supply bulk bins they are a grade 2 if the bolt has a gold color that is the grade 8

    @Chase- Yes, grade 8 bolts are usually yellow zinc plated, but that in itself is not an indicator of grade, since you could yellow zinc plate any grade. The head markings will indicate the grade, the plating is purely aesthetic.

    I have a bolt, with 3 grade 5 hash marks around the outside, and a triangle that swirls into the center. What kind of bolt is this?

    @Mike- The three hash marks indicate grade 5, the triangle with a swirl is the manufacturer’s stamp for Bowman Distribution. They are a distributor that has private label bolts made with their head mark.

    I have a bolt with HCZ and 3 hash marks with a line through them below that? is this a grade 5 or standard ya think?

    @John- Yes, the three radial lines indicate that the bolt is SAE grade 5. The HCZ would be the manufacturer’s identification.

    @Dale- 8.8 is a common grade of metric fastener that is similar in strength to an SAE grade 5 or ASTM A449 bolt.

    On a CSA explosion proof box do grade 5 NDF bolts meet electrical standard or are they always required to be grade 8 for 1/2″ and below.

    Dane,

    I came across some square head lag bolts where the only marking is a U on the head. They are also a golden yellowish material.. Any ideas on what I have.

    @Brad- I would assume that the U is a manufacturer’s marking. Lag bolts are not typically graded, so since there are no grade marks non your bolt I would have to say it is just low carbon, mild steel.

    @AJ- We are not sure why the writers of the SAE J429 standard decided to require the number of lines that they did. The standard was written decades ago.

    Hi I have a bolt with 6 dashes on it which I’m assuming is grade 8 and RC stamped on the head also do you know the manufacturer??

    @Brad- RC is the manufacturer’s stamp for Ningbo RuiChang Metal Products in Ningbo, China. And yes, six radial dashes is SAE J429 grade 8.

    Trying to find out what the letters BT on the head of a coach bolt (6mm diameter and approx 70mm length) might be. Any ideas?

    @John- I am sorry, but that does not immediately ring a bell. If you’d like to send in a photo, perhaps we can decode it for you.

    I have a bolt top of head says -FNL
    Center of head Has 9 dashes in the center
    Bottom of the Bolt says G9

    Wondering about the grade of this bolt

    @Jason- FNL is likely the bolt manufacturer, Fastenal. The G9 and nine dashes signify grade 9, which is a high strength grade slightly stronger than SAE grade 8. Grade 9 is a grade that was created to be a high strength alternative to SAE grade 8, but is not covered specifically by SAE J429 nor any other standards organization.

    I have a very old A286 fastener spec that refers to marking codes such as H19 and H28 on the head. We don’t know what that means. Anybody?

    have 1969 vet bolts holding rear spring have a w8 or wb on head corvette supplier sells grade 5 bolt as replacement are these strong enough

    @Paul – I am not familiar with a ‘W8’ or ‘WB’ marking on the head of a bolt, so I am not certain what grade they might be. Sorry we cannot help.

    Rivets removed and replaced with bolts at floorbeam connections on a truss bridge. All bolts and nuts are square….most have no designation, though some have a G in the center and other have an S off center.
    Any idea of strengths?

    @Sammy- Most off the shelf square bolts and nuts are just made from low carbon steel, similar to A307A/grade 2. If they were made to be high strength I would assume that they would have a grade marking of some sort, but the markings you describe do not sound like grade markings. I would assume that G and S are manufacturer’s markings, although they do not sound familiar to me.

    Trying to ID bolt head marking, which I think could be Monel K 500. Hex bolt mark is >.K.
    the dots are on the center line not at foot as shown in this comment.
    Thanks Baz

    @Barry Tyrrell- Apologies, but that mark does not ring a bell with us. Unless the bolt was made to an ASTM, ISO, or SAE standard, I don’t think there is a standard head mark to indicate Monel K 500. Sorry that we cannot help.

    i have a bolt with with A325 stamped on the top and NDF on bottom. Assume the A325 is ASTM a325 spec and NDF is manufacturer. Do you know what NDF stands for? What is the equivalent SAE grade for ASTM A325?

    @Daryl- I am sorry, but I looked thru my list of manufacturing marks, and I do not see NDF anywhere. As for an A325 equivalent, the closest would be SAE J429 grade 5, but I wouldn’t substitute without an engineering approval as they are some key differences.

    @Adeniyi- I am sorry, I do not know. Normally there is both a grade mark, and manufacturer’s ID mark. I am not aware of any grade that matches up with your mark, and I am not familiar with any manufacturer that uses that mark. Apologies.

    @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.

    @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?

    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

    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.

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