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Grade 8 v. SS bolts

centex77

Full Member
Joined
Oct 31, 2017
Messages
183
I agree, the Grade 8 plating does not survive on new bolts. I use SS on non-structural areas only (fenders, dash screws, etc.).

This is what I did. I like the look and it will resist rust better. I don't have to worry about moisture much where I'm at but after spending days with rusted bolts and nuts I'm eliminating it as much as possible. I hate rust. Everything under the body is grade 8 though purely for the strength factor. Overkill perhaps but I'm tired of working on this thing and I like impact wrenches.
 

sykanr0ng

Bronco Guru
Joined
Aug 11, 2014
Messages
5,363
For strength and corrosion resistance why not get Grade 8 (or F911) hardware and have it hard chrome or electroless nickel plated?
 

Digger556

Sr. Member
Joined
Aug 8, 2013
Messages
793
Zinc plating pretty much sucks for corrosion resistance. It's old tech. We use it because we have so little options.

The OEs use GEOMET or similar. There are a few places like Fastenal that sell GEOMET under their ECOguard name.

I would still use grade 8 or 10.9 metrics over stainless. Stainless can get the job done, but it's primary function is corrosion resistance. It is also prone to galling, especially in aluminum.

Be careful with exotic bolts. They may have higher strength, but the mfg may not disclose or realize the bolts susceptibility to environmental hydrogen embitterment.
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,229
Loc.
Upper SoKA
For strength and corrosion resistance why not get Grade 8 (or F911) hardware and have it hard chrome or electroless nickel plated?
Chrome plating would lead directly to hydrogen embrittlement unless the plater knows exactly what they're doing and does a bake-out within a very short time span of them coming out of the chrome bath. There's a Mil-Spec for baking out hardware after any type of electrolytic plating process out there somewhere if someone wants to do this.

Electro-less nickel can peel if you're not careful in choice of the plater. Ask any electro-less nickel plated Series 70 Colt owner. A good choice for electroless nickel-teflon would be Robar's NP3. Cal-Tech Plating is a mil-spec plating house that also does this process and straight electroless nickel, but they are strongly NOT recommended. Nickel-teflon is an awesome plating for corrosion resistance and dry lubrication, but your torque specs will need a radical reduction and don't expect self-locking nuts to still work that way.

Foremost states that their F911 bolts are made from 8620 alloy, so whatever environmental limitations 8620 has will apply.

I know of a robotics firm that had an unexpected failure of a pivot pin made from 17-4 H900. In air it is 200 ksi tensile strength with surprising ductility. This material makes a phenomenal bolt that will last weeks on a high volume production tombstone where a Grade 8 bolt in the same place wouldn't even last one shift.
10,000 feet down in the ocean it is not the same, the material experiences brittle failures in cold, saline environments. Something not well documented about 17-4. So could have the bolts made from 17-4 H900 so long as you don't plan on making your Bronco a submarine.
 

catfan

Contributor
Full Member
Joined
Jul 1, 2016
Messages
258
A buyer wanted all ss bolts on aluminum bump bodies where I worked,even with lube the nuts would seize up and twist off. It was a pain in the azz for sure.
 

JB Fab

Sponsor/Vendor
Bronco Guru
Joined
Mar 21, 2004
Messages
1,240
If you want to use a stainless bolt for your shocks, don't use generic hardware store stuff you have to be a bit more selective than "off-the shelf"

Source them from a domestic company with ISO 9001 and AS9100 Compliance
The type of stainless is as important as the way it was processed, IE, cold working most types of stainless changes the properties considerably. it is not uncommon to see cold worked stainless fasteners with a tensile strength of 180,000 psi (grade 8 =150,000) The way the threads are finished make a big difference on the heat generated during assembly (cause of galling).
The one thing all stainless fasteners have in common (assuming both mating parts are stainless), is that you have to reduce surface friction during assembly by using a lubricant and NEVER using a an impact or a motorized tool that turns faster than an air ratchet. The class of fit, IE aerospace fasteners with a class-1 thread fit will also be more prone to galling.


If you want to use stainless I would recommend
http://arp-bolts.com/


Jon
 

ntsqd

heratic car camper
Joined
Jan 30, 2005
Messages
3,229
Loc.
Upper SoKA
Pretty rare to see any production male fastener made with cut threads. Much faster and less expensive to cold roll them. Not to mention it makes a stronger thread.

Short of ARP SS offerings or one of the truly mil-spec varieties I've not seen a SS fastener with a tensile anywhere near that high. Maybe I'm not looking in the right place?
 
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