Stainless Vrs. Steel

[OutLaw]

I was wondering what was stronger: A Grade 8 Bolt or a Stainless Bolt. exact same bolt size wise. Which one will break first? Is the stainless more brittle than the grade 8? Or is it all around stronger? Does anyone know this answer? http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

[stealthcruiser]

me thinks the standard stainless bolt would be more malleable(softer),of course everytime i start thinkin',i get sleepy.

[Hot Rod To Hell]

There are a million different grades of stainless, so it all depends on the grade of it you are using. If you are wondering about engine bolt kits, or something like that, I would DEFINITELY go with ARP if yer gonna use stainless! I wouldn't trust any other stainless bolts.

[Fat Hack]

You'll have to wait for our official HAMB metalurigistologist to fill in the specifics on this, but stainless is more of a corrosion fighting thing than a strength thing. A grade eight bolt will be stronger than a stainless bolt of lesser grade...but if bothe bolts were the SAME grade, I dunno...

38Chevy454 knows this stuff far better than I, so he can answer that aspect of it...but I don't think that making bolts stainless serves any purpose other than to prevent rusting?

[OutLaw]

I was just wondering because to its a lot easier to cut a piece of steel rod than it is to cut a piece of stainless. I don't know because of what grade everything is or what. I would like to get a deffinate sceintific answer though.

[C9]

The average stainless bolt you buy - IE: 308, 316 alloy, marked on the top many times - is about a grade 4.

ARP has stainless bolts that are stronger than grade 8's.
Problem with them is the largest they have - last time I looked - was 7/16".

ARP's stainless high strength header bolt, 3/8-16 with 3/8" wrench head is a good one.
It's the same stuff as the high strength stainless.

Totally Stainless has high strength stainless bolts equal to grade 8's and in sizes for the rear of a typical street rod suspension.
1/2, 9/16 & 5/8".

There are some good looking and very high strength grade 9 bolts out there.
I believe they come in a black oxide or black chrome finish.
You'll have to do a search for them though, lost my bookmark.
If you decided to use these grade 9's you may want to ask about ductility.
I think it's entirely within limits for a suspension with things loaded in shear.

Note that a lot of factory suspensions use a quality grade 5 bolt.
More ductile than grade 8.
All of which means don't just blindly stick grade 8's on everything.

Be careful where you buy grade 8's as well.
Make sure they are USA made.
The offshore grade 8's sold at places like Orchard Supply and Home Depot are not up to the standards of American bolts.
In fact, USA made grade 8's have a paper trail following a particular batch of grade 8's back to the test laboratory.

And ... as much as I like Dorman Products, a lot of their bolts are made offshore nowadays.
All the more reason to buy your critical fasteners from ARP or Totally Stainless.

[OutLaw]

The bolts that we use are counter sunk 7/16 14 n/c bolts to hold a rear sprocket gear to the rear wheel ( Motorcycle ) The bolts that come with the kit are chrome plated ( and have no markings ) so we have to run a thread chaser over the threads to clean all the excess plating from the threads. Thats why I'd like to change to stainless.

[C9]

I dug through the Totally Stainless catalog and did not see high strength flathead (FH) allen bolts.
Which is what I think you are describing.

Couple of things you could do here.
If the sprocket is retained by 8 or probably 6 bolts more than likely the bolts thread into an aluminum hub.
Seems the stainless FH allens would do the job.
Make a point to check torque now and then to see if the bolt is stretching in use.

The other way to go is the black oxide coated FH allens.
I buy these locally in grade 5 and I believe they are readily available in grade 8.

If the sprocket and hub are polished or even brush finished aluminum the black bolts would look good.

You may want to do a search for ARP on the net, they do have a site and see if they have the high strength stainless FH allens.

[krupanut]

Hey Tyler, (sorry guys, stick em' up this is a post hi-jack!)

How are y'all coming on the coupe?
speaking of stainless, I've got a good 4 foot piece of 1 1/2
tubing for Jasons spreader bar I need to drop off.

[OutLaw]

There are 5 bolts and it a nut and bolt combo.

I'm looking for a graph or spread sheet of a test that someone probably a big company would have showing the results of a study comparing bolts ( stainless,grade 5, 8). Thats what I'd really love to have http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[OutLaw]

krupa we haven't touched it, but we have 6 bikes to get out this month.

[krupanut]

Six! Good deal! Let me know if y'all need some help.

[burger]

Outlaw,

An 18-8 or 316 SST bolt is about as strong as a grade 2 (unmarked head) plain steel fastener. Since the bolts you are using are unmarked, I'd say that it's safe to replace them with SST bolts. I would recommend using 18-8 as it's typically cheaper than 316.

SST bolts can be heat treated to be as strong or stronger than grade 5 and 8 bolts. However, this makes them brittle. Brittleness is not a desireable quality for fasteners. If you need the strength, use coated grade 5 or 8 bolts. If you really need to use SST (for corrosion reasons or whatever), step up to a larger bolt size for more strength. FWIW, the company I work for encourages us to avoid using grade 8 bolts in our designs as they're expensive. If we need the extra strength, we step up to a larger bolt size.

A few years back I put together an Engineering Standard for my company that's pretty similar to the spreadsheet you're looking for. My document lists torque values for threaded fasteners. The torque value is directly realted to the tensile and yield strength of the fastener, so you could extrapolate a strength comparision based on the the torque values. Give me your email address if you want a copy.



Ed

[burger]

PS- It's easier to cut plain steel than SST because plain steel is more ductile. With regards to fasteners, this is a desireable quality, because it means that the bolts will deform a little bit (sometimes elastically) before they break. SST bolts reach thier ultimate strength and snap.

[burger]

PPS- Both stainless and plain steel are considerably stronger than aluminum. If you're threading into aluminum, the tapped threads will likely fail before the fastener.

[John Copeland]

Outlaw,
I manage a testing facility that does a lot of threaded fasteners. Trust me, grade 8 fasteners are stronger that any stainless fasteners that you can buy off of the shelf. As many of the guys have already said, how strong do you need the fastener to be for your intended purpose. Any reputable fastener house can tell you what the load strenghts are for the different grade of bolts. There is a huge counterfeit business in threaded fasteners, especially when you also require a specific thread configuration. Grade 8, class 3 threaded fasteners are a huge concern with the military and the FAA. When you hear the horror story of the aircraft engine that departed the wing in flight, it's probably because someone installed a made in China, piece of shit bolt, that was passed off as being grade 8. Someone already said it, fastener lots will be identified by a control number, applied to and certified by the heat treat facility.

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