Bolt Head Markings: What do they mean? | Fasteners 101

[@anthonytuck864]

Great vid. One comment. The stainless bolts are not delineated by higher or lower grades. Each stainless alloy is typically designed to do a specific job in preventing corrosion. 304 is a basic 18/8 alloy that has a broad range of uses and is reasonably priced. 304 is also typically used in you house, kitchen sink, knives, forks etc. 316 has a small amount of molybdenum in it. Typically used in the food industry as it has excellent resistance to the acids found there. When using stainless bolts it is wise to understand strength of the specific alloys as their properties differ vastly from carbon steel bolts. The L appended to the end of the grade (IE: 304L) means that the alloy is low carbon and meets that specification. Happy days

[@AlbanyCountyFasteners]

Very good information to add! Thank you for your feedback!

[@creativity.studio4967]

Thanks. I was wondering because he left out so much explanation that is needed.

[@bubblywaters3116]

I just learned that you add 2 to the number of slashes on a bolt head to get the grade. 3 slashes add 2 and you have a 5 grade. Pretty cool. Always add 2 to the number of slashes for actual grade.

[@francoamerican4632]

This might seem like a radical concept, but wouldn't it make more sense to use five marks for a grade 5 bolt, eight marks for a grade 8 bolt, etc.

[@drgolfjim]

Thank you for getting right to the point.

[@holliwood3226]

IFI = Industrial Fasteners Institute. Just like any industry association their purpose is not to make it easy to decipher their markings. Hence "no marking = grade 2, 3 lines = grade 5, 6 lines = grade 8. Common sense does not apply when dealing with standards organizations.

[@foodstuff778]

Just add 2

[@solobassoon]

I have a specification on bolts saying: 'STUD BOLTS C/W 2 A4-70, ISO 3506-2, SF, HH...etc...'. May I ask what does 'SF' and 'HH' stand for?

[@dancorwin9232]

speed x 1.25. you're welcome

[@AlbanyCountyFasteners]

Thank you for your feedback.

[@brunotulliani]

Used a box of tissues because I was laughing so hard! It was better at 1.25x. You rock!

[@rickyhall1772]

Lol

[@bullfrogpondshop3179]

1.75 worked for me

[@danielnegrao6648]

Is cool, how about metric bolts? And Astm?

[@doncallangher6177]

Thanks for clearing this up for me, its something I've wanted to know since adolescence but too lazy too look up. So I guess, when in doubt, get a bolt with as many slashes as possible!

[@MoeLykit]

The Letter Codes on Bolts at Big Box stores from Bulk displays are Speed Codes for the Cashier to be able to identify them at the register

[@randygomez952]

This is absolutely fascinating lol

[@JesseGunzo]

Very useful info

[@lofivibes-techanimestudios281]

Hi, I am new in the fastener sales journey and I'd politely ask for advice to where start Selling Stainless Steel Fasteners :)

[@hoey3510]

Could some explain what f and 7 lines on a 5/16 unc bolt mean? Does it mean is stronger than a 6 line grade 8 bolt?

[@AlbanyCountyFasteners]

F is the manufacture mark and 7 marks may be OME made.

[@robertsims6136]

GOOD VIDEO. TY

[@rickconstant6106]

You don't mention metric bolts at all, which have a numerical system for identifying grades. Even in the US, most cars now are built using metric fasteners.

[@francoamerican4632]

Someday the rest of the world will come to their senses and convert to the system that is being used in the US.

[@CaniLupine]

I have metric bolts with 4 lines that secure my bottom motor mount, and I can't find any information on them.

[@macbethdemilo7253]

My stainless steel hex bolt has no dashes. Its has F593C JBK THE on the head. What grade is this bolt? Grade 2 since it has no dashes or something else? Thanks.

[@AlbanyCountyFasteners]

Correct! JBK THE is the manufacturer

[@macbethdemilo7253]

@@AlbanyCountyFasteners thank you, I got confused with the "grade 2" = no markings, and thought "but it has letters and numbers. I just wished there was a chart explaining what the F593C means.

[@AlbanyCountyFasteners]

Non available

[@francoistombe]

I have a bolt with 12 radial marks and an F in the centre. Where does this go on the ranking?

[@DonnieBeaver-j3g]

Don’t you mean hex head cap screw?

[@Finlandiabeach]

I have purchased Bolts marked "Fed-Alloy" With 12 markings. They were sold to me by Acklands-Grainger Industrial supply on sale. Are they the strongest bolts available?

[@AlbanyCountyFasteners]

The "strongest" bolts for commercial uses are usually Grade 8 (US) and Class 10.9 (Metric). We say "strongest" because a strong bolt can mean many different things. As far as the numbers go, these two boast the highest proof load, yield strength, & tensile strength of commercial grade bolts at the expense of ductility and a higher chance of fatigue failure over time. However, stainless steel bolts, while weaker in the numbers that make grade 8 and class 10.9 strong, have much higher corrosion resistance and can even resist salt water if the right grade of stainless is used. How do you define the strongest bolt?

[@Finlandiabeach]

@@AlbanyCountyFasteners Thanks for your response.

[@rickyhall1772]

Any bolt with more than 6 slashes usually indicates an alloy steel bolt or 'grade 9' bolt. They are comparable in strength to metric 12.9 bolts, but they are much harder to find.

[@dnolder1]

Thanks for answer on stainless bolts. I was just trying t figure where in automotive use I could use them. What are grade 2 bolts in comparison to tensile strength. Thanks

[@AlbanyCountyFasteners]

The Tensile strength of a Grade 2 bolt may vary slightly depending on size but will generally be about 74,000 PSI (1/4" - 3/4" Nominal) or 60,000 PSI (3/4" - 1-1/2" Nominal).

[@houndsmanone4563]

dnolder1, I don't know the tensile strength of grade 2 bolt but the fact that it has a lessor tensile strength saved my expensive rotary cutter when the blades hit a big stump in the ground. That single little bolt is the sacrificial part of my cutter therefore, I carry additional grade 2 bolts when cutting. Sorry, I know this didn't answer your tensile question but your question gave me a flash-back of when the snapped bolt saved my cutter. 🙂

[@crabjoe]

What is the difference between an A2 and A4 bolt? I replaced a bolt marked SRS 8.8 with one marked XXYX A2 S304. I was told to find one marked A4, but A2 was all I could fine. This is going to see a lot of road salt in the winters. The bolt is used to keep a DEF injector mounted to a diesel exhaust system. I figured any stainless bolt would be better than a carbide steel bolt, which I think was originally in there.

[@AlbanyCountyFasteners]

You're gonna want to find an A4 bolt to replace that A2 then. A4 is the metric equivalent to 316 stainless steel and A2 is the metric equivalent to 304 stainless steel. A4/316 stainless steel bolts are very corrosion resistant and are intended to be used in areas of high corrosion such as near salt water or heavily salted roads.

[@crabjoe]

@@AlbanyCountyFasteners Thank you.

[@bellini98-1]

@@AlbanyCountyFasteners 304 are actually more corrosion resistant in many environment, especially near sea water.

[@jerhughes75]

I have a bolt that nobody can tell me what they are. pretty sure they are grade 8. But head has 4 dots with IA on it. any ideas?

[@michaelwas8549]

Thank You!

[@andreazappaterra6763]

What is the acronym or the name company of JDF? Thanks

[@me1assassin]

How about "7T DS" where the 7T is abve the DS. Closest I coe is JIS, but appears non-metric 5/8-18? Very Confusig (on a tractor wheel stud)

[@thefogisgone3662]

Hello bob, the head markings expert haha

[@dnolder1]

How would you know what hardness a stainless steel bolt is?

[@AlbanyCountyFasteners]

There is no hardness to stainless steel and has no rating. Grade 8 bolts have a proof load of 120,000 pounds per square inch. The minimum strength of stainless steel bolts is 40,000 to 90,000 psi. The minimum strength of grade 8 bolts is 130,000 psi. Grade 8 bolts are much stronger than stainless steel.

[@BobbyKeeney-qw7zj]

Where can you bye a chart with Bolts

[@phiethoangthe7053]

I have a bolt with big letter H on Head, what does it mean? Thanks

[@AlbanyCountyFasteners]

Manufacture marking

[@UnknownUzer]

I came here hoping to find out the differences between the types of bolts, but all the information I got was how to convert slash marks into a number, but no actual useful information such as the strength differences

[@jacobhald1377]

As a european, used to the metric bolt markings, this seems so hard to grasp. 3 slashes grade 5, 6 slashes grade 8? Why not 5 slashes grade 5 and 8 slashes grade 8? The stainless marking however, makes sense i guess ^_^ Either way, good video, and now, should i ever happen to be in the USA, i would know my way around bolts! :D

[@iamoutofideas13]

Can you tell what the equivalent grade strength of a stainless steel bolt is by reading the markings on the head of the bolt?

[@therealcfiddy592]

No

[@davidbigelow5852]

The logo on the last Bolt is for Viraj Profiles out of India

[@Mark-gf7nl]

Great video! Thanks!

[@AlbanyCountyFasteners]

You're welcome! Thank you for your feedback.

[@Tjelection2024]

What does a 4.8 marking mean?

[@xiaohou8830]

I just purchased a standard GR 5 hex cap bolt from Fastenal and the mfg marking is FNL. Except for the FNL and the 3 strike marking, the head also has "HT". I checked the SAE J429 and did not see anything mentioned about such marking. Could it be "JH" as "FNL" is a sub-company of "JH"?

[@AlbanyCountyFasteners]

Possibly. Markings beyond grade or material markings vary from manufacturer to manufacturer.

[@OmarTheAtheistAziz]

Any way to buy a bolt knowing the girth of the threads, & the length of the bolt?

[@AlbanyCountyFasteners]

If by "girth" you mean diameter then yes! Bolts are sized based on their Diameter-Thread Pitch x Length. For example, a 1/4"-20 x 3" FT Bolt has a 1/4" diameter with 20 threads per inch and is 3" long, full threaded.

[@poncholo658]

I dont think anyone ever pay attention to bolt manufacturing. Just need to know how to tell what type of grade it is, what each different bolt colors mean and what each bolts purpose are made for.

[@t0mn8r35]

This would have been a better presentation if you had mentioned typical applications for each type of bolt.

[@robwilgenhof4386]

Thank you sir

[@kiengmeng7789]

Could you help me explain about symbol M, 8.8, and MICon cap bolt of china product?

[@AlbanyCountyFasteners]

The M means it's a metric bolt. The 8.8 is the grade and material of the bolt, in this case, carbon steel. The first digit relates to the minimum tensile strength of the material in megapascals (MPa), so that would be 800MPa, and the second is the yield strength in percentage, so that would be 80%. Lastly, MICon is the manufacturer's stamp.

[@friedensreich61]

@@AlbanyCountyFasteners I think I have a misunderstanding here. What I hear you saying is: Ultimate tensile strength (UTS) = 8 N/mm^2 = 8 MPa and YS/UTS = 0.08. Both does not make sense. Could you please clarify what you actually mean.

[@AlbanyCountyFasteners]

@@friedensreich61 Hm...that response may have been in error. We've updated the comment to clarify what the 8.8 represents. We apologize for the confusion!

[@friedensreich61]

@@AlbanyCountyFasteners thanks for the quick clarification. I would even formulate that the first digit is the min. tensile strength in 'hundreds' MPa and the second is the ratio 'tens' of percent. But with the numbers you provided, very clear indeed.

[@noekimes1887]

What do that markings (F593G316 THE) mean?

[@kandasamyrajan]

Thanks

[@AlbanyCountyFasteners]

Your welcome!

[@timlower89]

Just curious, is there a reason they complicate bolt markings? 3=5, 6=8. What’s the philosophy behind this, instead of just saying 3 is not as strong as a 6? Normally there’s a reason behind it, so just curious. Funny how bolts go up in numbers when stronger, but in electrical wiring the thicker the wire the lower the number. Sorry to be a pain in the ass, one of those questions that always makes me scratch my head.

[@AlbanyCountyFasteners]

The grade markings were decided by the Society of Automotive Engineers (SAE) under their J429 specification. As far as we're aware, there's no particular reason that they are set up this way; it's just what SAE decided on when they made that spec. The general rule of thumb is that the grade is 2 less than the number of marks. Sorry this isn't exactly the most informative answer. I can't find anything about why those numbers of markings were chosen specifically.

[@krzysztofborowiak3088]

Most probably because the 3 & 6 dash markings are symmetrical thus easy to identify without the need to count marks. Grades 5.1 & 5.2 have markings on one side, closer to each other. Same for grade 8.2

[@frankd.brennan6520]

Can I use a stronger bolt for a head gasket on a car

[@justinc9911]

nice to know, I have a bolt with "h110" on it? what does the "h110 stand for?

[@AlbanyCountyFasteners]

Sounds like that might be a manufacturer's marking. What kind of bolt is it?

[@gsh319]

Said a lot but learned just a little..... I knew this info coming in, thought there’s more to learn.

[@chadbosko8935]

You don't seem to be telling us what the different grades mean, say what 6 lines and a P would mean,I just took it from the auger on my snowblower, I am thinking this is not a shear bolt, there is no groove in the bolt, help

[@fredytay2122]

Thanks😎

[@AlbanyCountyFasteners]

You're welcome! Thank you for your feedback!

[@hussainali9999]

Standard engineers “let us make something to make there life harder” ok let’s make unreadable marking on bolts heads

[@hiallthr]

Hi, can i ask what difference between FKE and VIBO?

[@FEDAMachine]

Nice

[@RespawnRestricted]

I have alot that have 8.8 on them is that grade 8.8?

[@rickyhall1772]

Metric grade 8.8 is similar to an sae grade 5 bolt.

[@markharrisllb]

Are these international marking or just American please?

[@rickyhall1772]

They are sae or American bolt markings. Although some metric like torx and e-torx are starting to use the same slash marks to indicate strength.

[@billhamilton2366]

Nicely manicured hands of the presenter.

[@AlbanyCountyFasteners]

Thank you for your feedback.

[@DaveM2]

Manifacture?

[@honda110wave2]

i really like bolts us torque specs

[@sanbell6951]

All my garden tools are 304s

[@victorvillacis6764]

its 3am in the morning and I am learning about bolts.....I work in software smh lol

[@henryarce6547]

Quarter 20 cap?

[@richardtemby4358]

It would have helped if you explained the various grades by number or maybe you are not familiar with them. Just sayin!!!

[@Lotrioni]

First thing first. What is IFI

[@AlbanyCountyFasteners]

IFI is the Industrial Fasteners Institute. They help define many fastener standards and their reference guides are often used by engineers to check fastener specifications.

[@ckinc89]

Thank Q

[@willsrestorations]

For six and a half minute video you gave almost zero information. it would have been nice to let everyone know what the strength of the bolts are what they could be used for, weather the automotive or if it's corrosive or non corrosive.

[@AlbanyCountyFasteners]

Thank you for your feedback.

[@honda110wave2]

bolts united star number one

[@JustMwah]

👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻👍🏻

[@DUNEATV]

Ehhh forget about it....

[@hyperhektor7733]

3 slashes grade 5 6 slashes grade 8 yeah american measurement systems xD

[@lacausa2000]

Our measuring system is called the Imperial Measurement System - it was developed by the English

[@hyperhektor7733]

@@lacausa2000 i know and i feel empathy for you :), (i am lucky i need this just for plumbing, you need it for everyday stuff)

[@rickyhall1772]

Well in terms of bolts, metric have 5.8, 8.8, 10.9, and 12.9. can you explain what the decimals indicate? Because they don't indicate tensile strength, so they could have picked 5, 8, 10 and 12 just like sae picked 2, 5, 8 and 9

[@zzzyyyzz]

only american bolts here..

[@woofdoogy]

Mannnafature mahhkings

[@AlbanyCountyFasteners]

Thank you for your feedback.

[@karenhill3356]

When you get back from the Capital...

[@bonlappen3000]

There's no logic to that! 3 marks should be grade 3 and 5 should be 5 and so on

[@car5car5]

The guy has very high blood pressure and partially blocked neck arteries. This should explain his zero knowledge of metric markings, which I really needed to know. So stop eating junk and make video about metric bolts.

[@r.handoko7775]

That product manufactur from.china

[@AlbanyCountyFasteners]

Thank you for your feedback.

[@donsimons9810]

Designed elsewhere.