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Grade 8 v. SS bolts

Howard2x4x4

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Apr 19, 2014
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Any opinions regarding bolts? Today for shock installation, later who knows. I've heard that SS bolts are brittle. Opinions please!!! Howard in beautiful west Michigan
 

AZ73

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You're comparing apples and oranges kind of. Grade 8 is about shear strength. SS is about rust protection. Typically a Grade 8 is also zinc coated to prevent rust. If you use SS, you have an issue of galling if you screw them into a different type of metal without some kind of thread coating on them. That being said, I used all Grade 8 nuts and bolts simply because of my desired to have the yellow zinc look. All my screws (for exterior lights, trim, cover plates, etc) are SS to prevent rusting.
 

B RON CO

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Hi, I would be careful with stainless steel bolts.
If you have a boat in salt water you have to be careful.
Some marine grade hardware containes ferrous metal,
ie magnetic steel.
I like grade 5 and grade 8.
Good luck
 

Broncobowsher

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As mentioned above, Stainless is not considered a structural steel. Not typically brittle, but not rigid. Galling is a common issue.
For a common shock bolt, grade 5 is going to be stronger than the bracket or the welds. Grade 8 is just extra expense, but will work just fine.
 

Nothing Special

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.... If you use SS, you have an issue of galling if you screw them into a different type of metal without some kind of thread coating on them....

Actually galling is a bigger problem if you uses stainless in the same type of metal (stainless nuts on stainless bolts). Anti-seize is a MUST! Using a steel nut (I use grade 8 for the zinc corrosion protection) on a stainless bolt is a lot easier to loosen later.
 

broncodriver99

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I have given up on SS bolts pretty much completely. Unless you buy quality bolts from a traceable vendor they seem to be junk, and even quality bolts have their issues. I have had galling issues even when using anti seize and quite a few the heads just popped off. Grade 8 is oversold as well. If the original application used a Grade 5 bolt there is nothing wrong with replacing it with another quality Grade 5 bolt, but I would definitely use Grade 8 over SS.
 

ntsqd

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In practice, SS is Grade 2 at best. Not brittle at all, very malleable - and that's its problem.

Galling on LIKE metals, galvanic corrosion potential on UNLIKE metals (aluminum being just about the worst case). Buy them passivated if you can find them offered that way.

Grade 8 is the brittle one (relatively speaking). If you really want or need strength go with F911 bolts. Strength and Ductility both exceed a Grade 8. They're close to being a Holokrome Socket Head Cap Screw with a hex head.

Whole lot of education to be had in Carroll Smith's "Screw to Win" er....... "Nuts, Bolts, Fasteners, and Plumbing" book. Smith was "the other Carroll" at Shelby Racing in the 60's.
 

cldonley

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The rust preventative in SS is nickel. The higher the nickel content, the more rust prevention and the less durability. Stainless steel screws in aircraft panels are often drilled out because the phillips head rounds off because it is soft. High end SS bolts and screws can't be picked up with a magnet because of the high nickle content. So, in short, this aircraft mechanic hates SS hardware. Grade 8 has the coating necessary to prevent corrosion, is stronger than virtually every part you'll use it in on the truck and won't let you down. Sorry for the rant...wish I had all the time back I've spent drilling out SS hardware!:mad:
 

ntsqd

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It's actually the chromium in SS rather than the nickel that gives it the chromium-oxide surface film that is most effective in preventing corrosion. Nickel may play a part, but it is not the leading alloying element in this. Passivation is a process to create that film. I have seen unpassivated SS screws rust in a salt water environment.

https://www.besttechnologyinc.com/passivation-systems/what-is-passivation/

Locally my G8 sources don't seem to be getting hardware with quality plating. In this coastal desert they last only a year or two before they start to rust. Used to be that they'd almost never rust unless taken down to the ocean itself.
 

Bronco4x4

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Messages
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I agree, the Grade 8 plating does not survive on new bolts. I use SS on non-structural areas only (fenders, dash screws, etc.).
 

cldonley

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I've noticed that too from locally sourced Grade 8. Is there a better place to get them?

Aircraft Spruce- http://www.aircraftspruce.com/menus/ha/bolts.html

It's also helpful if you install them with lubricant to keep from damaging the coating when installing. Cadmium plating is great and very durable when it is properly applied. Unfortunately it is becoming harder to find quality hardware not infiltrated by the Chinese knock-offs.
 

broncodriver99

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Cadmium plating is great and very durable when it is properly applied. Unfortunately it is becoming harder to find quality hardware not infiltrated by the Chinese knock-offs.

I think that is part of the problem. Didn't Cadmium go away because of environmental issues? I believe everything now is Zinc either of the yellow or silver(natural) variety.

I totally agree on the Chinese knock off hardware though.
 
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