nuts and bolts

[CamaroAJ]

just thought i would ask before i wasted the money on something that won't be the best for the project. i want to use all stainless hardware on the camaro the only parts i'm concerned with is the control arm mounting bolts, is stainless stronger than Grade 8? i'm new to the stainless and grade 5 and 8 stuff, my race bike was all aluminum and ti nuts and bolts. sorry if it seams like a dumb question

[CarlC]

There's only two companies that I would consider using: ARP and SPS.

Even so, using stainless fasteners in a structural application (A-arms, leaf springs, etc) is a no-no. The better option is to use a quality Grade 8 bolt, not the standard hardware stuff.

Chroming structural fasteners is also a no-no.

I use AN type aircraft airframe bolts from Aircraft Spuce. They are Grade 5, but the grip length can be tailored so that the threads are not in shear. This makes the connection as strong as a G8 bolt but the bolt quality is the best there is.

For a really good lesson on fasteners pick up a copy of Carroll Smith's "Nuts, Bolts, Fasteners, and Plumbing." It has a lot of great fastener and fabrication information.

[68LSS1]

There's only two companies that I would consider using: ARP and SPS.

Even so, using stainless fasteners in a structural application (A-arms, leaf springs, etc) is a no-no. The better option is to use a quality Grade 8 bolt, not the standard hardware stuff.

Chroming structural fasteners is also a no-no.

I use AN type aircraft airframe bolts from Aircraft Spuce. They are Grade 5, but the grip length can be tailored so that the threads are not in shear. This makes the connection as strong as a G8 bolt but the bolt quality is the best there is.

For a really good lesson on fasteners pick up a copy of Carroll Smith's "Nuts, Bolts, Fasteners, and Plumbing." It has a lot of great fastener and fabrication information.

I have a couple questions about your post. I got some SS hardware from Totally Stainless that exceeds grade 8 specifications (for my trailing arms). What is wrong with SS in "structural applications" as you put it? I agree that I would not go down to the local hardware store or Lowes to buy my SS hardware though. And as far as changing the grip length on a grade 5 as to not put the threads in shear, I don't follow this. How can a grade 5 become a grade 8? Bolt strength is bolt strength, irregardless of length right? Apparently your saying not. I will try and find a copy of that book because it seems like there is not a lot of knowledge out there on fastener strength and application. As a aircraft mechanic this topic is covered very well in our tech pubs but it doesn't seem to be in the automotive industry, especially the performance orientated aftermarket.

[myclone]

As was stated stainless should not be used in anything structural. People have a misconception that because stainless steel has good corrosion and heat resistance properties that it is super strong and will hold up to anything. In reality stainless steel is pretty weak compared to a quality grade 8 fastener.

The "grip length" that was mentioned is basically spec'ing the bolt so that the unthreaded shank portion takes all the shear load and the threads are outside the shear plane. What that all means is that the stronger unthreaded shank of the bolt is taking the shear load since it is physically bigger than the cut down thread portion. A 1/2" unthreaded stainless road has quite a bit more shear strength than a piece of 1/2" threaded rod since its really no longer 1/2" in diameter due to the cutting of the threads.

Ive worked with stainless bolts every day for the last 10yrs and absolutely hate stainless steel bolts. They are porus and tend to fuse themselves to whatever they are screwed into over time when subjected to heat cycles and/or corrosive elements. That also means that if over torqued in the least the threads easily gaul(sp?) which ruins the fastener. Last but not least is the fact that stainless is pretty soft and when a lot of torque is applied the fastener breaks, the head strips, etc, etc. The only reason we continue to use stainless steel where I work is due to the tempratures involved and stainless steels ability to survive it (for a while at least).

Stainless is fine for attaching brackets, fenders, and other non structural applications but anytime there will be a significant load a grade 8 mild steel fastener wins hands down. There is a reason that rod, head, and main cap bolts arent made from stainless steel.

[MuscleRodz]

Bolt grades are determined by the alloy the bolt is made from and how much it is tempered. Grade five bolts should be used for non-stressed applications. They have a shear loading of around 90,000 psi if i remember right. Grade 8 is around 150,000 psi I think. Grade 8 is equivelent to AN hardware used in aircraft aplications.

Stainless is naturally softer than normal steel due to its nickel content. I would not use in structural application either. ARP does make some bolts they claim to be higher strength than grade 8. I would research further because if it becomes to hard, especially in a impact load situation, the bolt could shatter rather than bend.

Mike

[CarlC]

I'm in agreement with myclone.

For critical joint fastening look to the aerospace world. There's not a design out there that uses a stainless fastener for a critical structural application. Suspension components, including pivot bolts, and brake mounting points are the most important bolted features on our cars. Fender mounting and exhaust hanging are a whole different deal.

ARP does offer a stainless fastener that is rated in the G8 range. However, until I see fatigue life tests in comparison to a proper G5 or G8 I'll shy away from them. Plus, their ease of galling makes them less than desireable for applications that need periodic disassembly. Unless ARP has increased their offering they offer very few of the sizes required for GM suspension mounting points.

The minimum rated ultimate tensile strength of a properly made and spec'ed AN bolt is 125 ksi. Typical G5 is rated at 120 ksi, G8 at 150 ksi. A properly designed 1/2" double shear AN bolted joint has an allowable shear rating of over 25,000#. I'll trust this over a no-name G8 bolted joint any day.

If you want the best of anything (bolts, pistons, tires, etc.) don't let the distributor steer you down their path. How many of us call up our favorite parts house and say "give me pistons"? We know what we want before the call is made because if we leave that decision in the hands of the distributor we get what they want to sell us, not what will best fit our application. Same deal with critical fasteners. When in doubt call the manufacturer and get a spec. sheet. I doubt that the Chinese no-name products will have any specs. available. Even if they did would you trust them? You can't go wrong using GM bolts either.

[68LSS1]

ARP does make a G8 SS bolt. The 12 pont ARP SS bolt is rated at 170,000 psi. I do believe that the average SS bolts are slightly better than a G2 and I agree one should be careful as to the supplier of such fasteners. As to not using them in the aerospace industry I would guess to be because 1) most bolts that are used in structural applications are also used with bushings or bearings, 2) dissimilar metals issues, 3) cost, i.e. why pay for a "pretty" bolt? and 4) they are a pain to use (galling issues like previuosly stated). I think most people that would like to use SS fasteners on their vehicle are looking at the aesthetics of it also. Most of the points that are being made I agree with. I think that the SS industry has come a long way from back in the day of the G2 SS fasteners used on trailer queens and show cars. If nothing else, in a year or so I'll let everyone know how the SS trailing arms bolts hold up to 7-800rwhp nitrous launches and some local road course stuff. If I'm wrong I'll admit it but the specs that ARP and Totally Stainless are giving are showing "some" SS fasteners that EXCEED G8.

[RobM]

i only used ARP 12 point ss cap screws to bolt down my polished intake manifold and some brakets to my polished water pump. and the only reason i used them was for looks and i knew that the aluminum parts would fail long before the bolts did. I was also sure to use a liberal amount of anit-seiz compound so the bolts wouldnt gaul. if the part has a load on it and is visable i use a mild steel grad 8 and paint the head black with touch up paint so it wont rust and looks decent.

[Jagarang]

There was a discussion regarding this issue recently. Try the search engine and you should find it.

Fruitless search attempted.

HMMMMM...I just tried and apparently not as easy to find as I'd hoped. Perhaps someone remembers where it is.

[Fuelie Fan]

http://www.ssina.com/download_a_file/fasteners.pdf

[PAI Racing]

Check out Carroll Smith's book "Nuts Bolts and Fasteners". Coast Fabrication in Huntington Beach supplies a lot of IMSA/ChampCar/Indy type teams and has a very nice selection of hardware. They have a web site.