Kinda OT Fasteners - Are all Grade 8's the same?

[HoosierBuddy]

Hey guys,

Sorry to hit you with a non-tool question...and sorrier still that this is work related. This relates to a turbocharger on a backhoe. The factory mounting bolts broke. Their tech line suggested we replace those bolts with Grade 8 to prevent the problem (which I guess is common) from reoccuring. Did that.

They broke again.

My mechanic is scratching his head. I suggested maybe he should use a torque wrench this time when he installs them. However, I'm not convinced that is going to be a game changer. What I'm really wondering is if these Grade 8 bolts I'm getting from the local hardware store (which they buy from a distributor who likely buys them from an importer) are the real deal.

Or...am I overthinking this thing. Are all Grade 8 bolts the same?

Phil

 

[Stick]

Supposedly they all meet ISO standards, but I've noticed a difference between hardware store bolts and those from a quality distributor like Lawson or Bowman. And even then, the ones from Caterpillar seem higher quality than even those.

 

[Monte]

try grade 10 ?

 

[Sancho]

There was a book available free online for a while called "the Nasa fastener design guide" or something similar. It goes into some detail on why grade 8 isnt always grade 8.

Suffice to say, Stick is correct. Not all are equal.

 

[BrokewrenchLS1]

try grade 10 ?

10.9 is the metric equivalent of imperial Grade 8, yes?

 

[jjjrmx5]

Hey guys,

Or...am I overthinking this thing. Are all Grade 8 bolts the same?

Phil

In theory, they should be.
The standards, quality and tests to which fasteners are measured against provide strict parameters as to what is required to meet a certain grade.

I can say that with a "but", because I have been involved with mfr. and assembly where fasteners were/are ordered by the case and pallet in all sizes from M5 to M14 and most std. sizes as well.

Our supplier was a wholesaler who bought high quality and high grade fasteners in a zinc finish as well as stainless for us.

I guess in an attempt by the distributor to cut costs, and possibly unknowingly, we began to suffer problems of threads stripping and heads breaking off of both the M6 phillips head screws and M6 bolts he was providing us with.

A little research on his end gave him the answer that the company he was buying from had outsourced the fastener production to China and that either the metal quality or the mfgr process had changed resulting in an inferior fastener. The supplier was changed and a different fastener was spec'd and we never had a problem after that.

So, to make a short story long, I;ve seen new fasteners supplied that are said to be listed as or stamped to meet a certain spec, but not "really" meet that standard. I;d love to say they are all OK, but unless you buy from a second party source that knows what they sell or have tested it I like to buy from the OEM or OEM local dealer to ensure a high quality good.

 

[benny27]

did you use metric bolts they are graded different 8 (8.8) is more like a 5 you would need 10.9 if it was metric

 

[Joe B.]

Supposedly they all meet ISO standards, but I've noticed a difference between hardware store bolts and those from a quality distributor like Lawson or Bowman. And even then, the ones from Caterpillar seem higher quality than even those.

That says it all. They will all meet the standard but some may be better than others. Can you show us a pic of the head markings on the one that broke?

It is unlikely that you received a miss marked bolt.

Was it a AlliedSignal/Garrett/Honeywell turbo? I spent about 4 years ending about 10 years ago as their primary fastener vendor.

Usually when you have a failure like this the problem is not a problem with the quality of the bolt. It usually stems from something putting undue stress on the joint or an inadequate design. It seemed like I was always sending bolts to an independent lab to prove that they were not the cause of a failure. I never did see a lab report showing anything wrong with the bolt. (Granted, my company mainly bought from good suppliers.)

 

[browntown]

I was thinking there was a class 10 bolt, but I guess the metric class 10.9 bolts are what I was thinking of which are equivalent to grade 8's. While I was figuring that out, I saw a post on a honda board " dont use any SAE graded bolts. I only trust AN graded bolts... There is no enforcement of SAE grades, no batch testing. AN graded bolts are batch tested and the only thing the FAA allows to be used in aircraft.."

Obviously some random board post isn't something to swear by, but when looking through fastenal, they have grade 9 bolts that are supposedly even stronger in the tensile department and some specific high heat astm rated bolts.

 

[Monte]

10.9 is the metric equivalent of imperial Grade 8, yes?

i think yes.
"8.8" is good, "10.9" would be better, "12.9" is best.
First digit multiplied with 100 is the tensile strength so in case of a 10.9 grade screw the tensile strength is 1000 Newton/mm² (10 x 100). The first digit multiplied with the second digit multiplied with 10 (10 x 9 = 90 x 10 = 900) is the yield strength/tensile yield point in N/mm².

 

[Vinny]

I had a 12.9 snap on me (in a very bad place) without that much pressure. Sometimes you get bad bolts.
On this topic, though, whats a site that sells high quality bolts AND sells singles? I'd love to buy from McMaster or Fastenal but they only sell in bulk.

 

[theoldwizard1]

This relates to a turbocharger on a backhoe. The factory mounting bolts broke.

Interesting. Is the bolt in shear or tension ? Over sized holes for shear applications put additional loads on the bolt.

Any chance of drilling a large hole for a bigger bolt without compromising the mounting tab/flange ?

I suggested maybe he should use a torque wrench this time when he installs them.

Good suggestion. Could he be overtightening ? If so, use some high temp thread locker and keep within torque specs.

Or...am I overthinking this thing.

My gut tells me there is something else wrong. Could it be some kind of vibration issue ? When things start vibrating at their "natural harmony" bad things happen.

Would some kind of additional brace help eliminate some vibration ?

 

[dabirdguy]

Tractor Supply got sued a while back for selling grade 8 bolts that tested out at lower grades.

 

[woody 73]

Wow I am thunder struck I thought all grade 8 bolts were of the same high standards and having them snap in two so easy is very odd. I bought a few boxes from msc and I never had any break; could it be that the op got a bad batch from the factory?

 

[Wakefield]

I remember reading stories about counterfeit (as to grade and brand) fasteners.
I understand that as to torque,if it is too loose it can fail in vibration more easily.
I imagine the turbocharger gets very hot. Expansion-stretching?

 

[djjsr]

I think there was a pretty big problem about 10 years ago with counterfeit fasteners getting into the supply chains, including the government. I don't know what ever happened to all of the junk stuff but I'm sure there's still some out there somewhere.

Guess where it came from.

 

[Travis E.]

I had a 12.9 snap on me (in a very bad place) without that much pressure. Sometimes you get bad bolts.
On this topic, though, whats a site that sells high quality bolts AND sells singles? I'd love to buy from McMaster or Fastenal but they only sell in bulk.

Fastenal in Simi will sell singles.

 

[Vinny]

Really? Huh. Thanks Travis.
To add to this thread, I think I posted about it in another topic, but I bought brand new versions of these pointed bolts that are used to pierce the body to chassis seal on a VW. I wanted all new hardware. I'd say five or six had the threads destroyed in the process of tightening them. I took all of them off and went with the originals, which were rusted, gummed up, and looked like hell. No failures.
Definitely something bad about new bolts. Now I hit the junkyards for what I need rather than replace things. Cheaper and better.
For what it's worth.

 

[amolaver]

i've bought small numbers (packs of 5 or 10) of high quality nuts and bolts from mcmaster before and not been dissapointed. they are awesome to deal with, the online catalog is awesome, and their shipping time is incredible (and cheap - ~4lb of fasteners cost me $5).

as others have stated, SAE grade 8 is similar to metric 10.9 - not exactly the same, but pretty dang close. there are references online, and especially in a turbocharger application, you should be concerned about the fastener's performance at elevated temperatures. again, the online references describe what the standards dictate - hell might even be on wikipedia.

ahm

 

[Ric in Richmond]

Great book....all of his are.

http://www.amazon.com/dp/0879384069/?tag=atomicindus08-20

 

[CHRIS LUCKYMAN]

I used Fastenal hardware for a few years, never had a problem. Then, the Wurth guy started coming around. Free hardware cabinets (with the purchase of a shitload of hardware), free lighters, pens, notepads. Gave me the whole rundown - our 8.8s are actually closer to 10.9... I switched over completely to Wurth.
I was putting together a transmission that had a lot of 13mm bolts. The heads of 3 bolts just spun off when torque-ing them down. What the ****? Never had that happen before. So... I started going through the receipts for the fasteners from Wurth... the **** was priced super high. I threw some bolts in the vise and used a breaker bar to "test" them, Wurth bolts were junk compared to Fastenal. I was pissed. When the Wurth guy came by to "check the inventory and reorder anything that was low", I chewed him out. He came by a couple of months later, saying that their pricing rates were lower, I told him to kick rocks.
A little off topic, but definitely, not all hardware is created equal. I did keep the cabinets... they're pretty cool.

 

[blue dog]

F911

http://www.f911.com/fore4.html

 

[CHRIS LUCKYMAN]

F911

http://www.f911.com/fore4.html

When their website selling "the best hardware" has lots of spelling errors, and punctuation errors, I tend to err on the side of curb-kicking.

 

[NUTTSGT]

I've wondered if the stuff from TSC isn't coming from China and if it's up to par.

 

[plinker]

Maybe try Lawson? I Have heard they are really good bolts.


The local Fastenal here sells individual pieces as well.

 

[larry_g]

Years back on the wheat farm my brother stocked only Cat bolts as their main equipment was Cat. On day a bolt salesman dropped by the shop trying to get his business. Jack asked if he had a 1/2" bolt and nut. The salesman produced one and Jack grabbed the bolt head with the vise and put on a stack of flat washers and the nut. He hit it with the rattle gun and proceeded to break the bolt. The salesman protested so Jack grabbed a bolt from the bin and set it up the same way. He handed the rattle gun to the salesman and he went at it. The Cat bolt did not break. So I have to agree with Skin that Cat bolts are the ones to get if you need good ones.

As for the origional problem I would check that turbo real close for imbalance, overheating, warped flanges or other problems. How many hours on the engine/turbo?

lg
no neat sig line

 

[speed bump]

If you need stronger bolts Fastenal sells grade 9 and Cat bolts are rated higher than grade 8 as well.

As far as breaking bolts there are dozens of potential reasons why it could happen beyond the fastener itself. If I was consistently breaking bolts in a certain application I would start looking for a solution that was a game changer rather than hoping I found strong enough bolts.

 

[diesel research]

Look into fabricating a turbocharger support bracket and or taking suome of the exhausts hanging weight off of the turbo by using better exhaust supports. Finally, ensuring the engine mounts are sufficient and the exhaust has some flexibility joint somewhere.

 

[larry_g]

As I thought about this problem of the turbo I would really question if one wants to oversize the fastener or up its strength. Doing so will cause the next weakest link to fail which would be t he turbo or the exhaust manifold. Unless this is a knowm problem with your particular setup then I would look for the root problem here. If you have thousands of hours running on this engine then why did it fail now? Is there a new exhaust system on it? New turbo? What was the last major work done around the turbo? The last work done is a good place to start looking for problems.

lg
no neat sig line

 

[Joe Mamma]

Great book....all of his are.

http://www.amazon.com/dp/0879384069/?tag=atomicindus08-20

That's a great book Ric.

I definitely do not think all grade 8 fasteners are the same. Also, I generally assume that any grade 8 bolt (or any SAE bolt) is counterfeit and/or low quality unless it (1) came off of (and was originally installed on ) a quality product, like a car or good tractor or (2) the bolt is marked with a manufacturer's symbol (and it doesn't look like a counterfeit).

I never completely trust any threaded fastener that I buy at a hardware store (unless it's got a good manufacturer's mark).

Here is one place to go for quality fasteners (I have no ties to this place):

https://www.pegasusautoracing.com/advcat.asp?CategoryID=HARDWARE

Joe Mamma

 

[HoosierBuddy]

THANKS for all the great advice guys.

This is on a Case 580 Super L backhoe btw with low hours.

I sort of agreed with the advice given about "there must be another problem". So, I had the dealer mechanic swing by and look it over (he's about 30 miles away...so I don't just do that on a whim.)

He said the problems with the broken bolts ARE (in order of priority).

1. Bolts installed without washers under the heads. (No washers are shown on the bolt callout in the service literature...but he assures us they are there from the factory.)

2. Motor mount shot causing engine to move around too much putting stress on bolts.

3. Idle set too low causing excessive vibration.

While he was here he looked at pins and bushings on the hoe attachment and we decided it's time to do service on all of that too. The machine doesn't have a lot of hours on it, but a lot of what it has done has been with a rock hammer attachment...which is hard on the pins and bushings.

Since we're having him service it at the dealer, I'm sure it will come back with factory turbo bolts. Hopefully that will be the end of that problem!

Phil

BTW....I want to point out that I REALLY APPRECIATE you guys taking the time to not only answer my question, but point out that the answer to my question WAS NOT the answer to my problem! This forum rocks!

 

[Outlawmws]

I was in aerospace for quite a number of years, and can verify that counterfeit fasteners (meaning fasteners that do not adhere to the standards) have been an issue for at least 20 years. Ever since the Chinese started flooding the markets with ****. It got into the mil spec supply chain affecting the military, aircraft producers, and even the space programs.

The "Vise test" mentioned earlier is one way, using a torque wrench for destructive sample testing is another.

As to the OP's particular issue, harmonic vibrations can and do cause perfectly good fasteners to break. I've had it happen on cars, and a turbo is a nice high speed rotating assembly that can generate a bad harmonic. ( I had a high winding 1600 Kent motor that would either break or vibrate loose the exhaust manifold bolts at both ends until I managed to get high grade fasteners and added locking mechanisms to keep them tight...) Without seeing the assembly I can't make any practical suggestions or guesses, but I would definitely take a look at the fasteners being supplied first.

 

[Vinny]

Here's what I wonder: I find bolts at the hardware store that have the same manufacturer logo as stock stuff on my cars. What I wonder is if these bootleggers are just throwing the logo on their products, or if these places have dropped their own standards. Because I sometimes will wreck one of these new bolts and its original rusted and beaten piece holds strong.

 

[Outlawmws]

Here's what I wonder: I find bolts at the hardware store that have the same manufacturer logo as stock stuff on my cars. What I wonder is if these bootleggers are just throwing the logo on their products, or if these places have dropped their own standards. Because I sometimes will wreck one of these new bolts and its original rusted and beaten piece holds strong.

The answer to that is yes they do.

 

[Cryo Gal]

http://www.choice-distribution.com/bolts.htm
http://www.umufc.org/BoltCounterfeitSuspectList.htm

 

[Wrenches of Death]

When their website selling "the best hardware" has lots of spelling errors, and punctuation errors, I tend to err on the side of curb-kicking.

Mabee thay're injuneer was off that day.


WoD

 

[Givl Reggin]

Are all Grade 8 bolts the same?

The way these are hardened is that the bolts are placed in a basket, probably 100,00 pieces (or more) at a time, heated in an electric oven for a period of time then cooled. The manufactures don't like to admit it, but there is a great deal of variance, depending on just where the piece was in the basket and how hot it got and how quickly it got quenched. When you're dealing with that many pieces you can easily see how some are going to be out of spec... it's really unavoidable with this method. And it's not just nuts and bolts, it's anything that is heat-treated in batches; wrenches, hammers, screwdrivers, etc.

 

[catsteve]

+ 1 on CAT bolts

Your local Cat dealer will sell singles. Cat hardware seems to be more reasonably priced than you expect.