Using chrome or stainless steel bolts and their grade

Picked up some chrome bolts for another car project as they looked very shiny. This got me wondering what “grade” such bolts were made of?

Also knowing that some of us interchange stainless bolts when doing projects, are they too up to the strength requirements of are cars. I think some shiny stainless would look nice on the suspension parts.

Final thought. When replacing bolts and nuts would you as a matter of course recommend using anti-seize lube for future rust free removal if necessary.

Gerard

I use Stainless when the fastener isn’t highly loaded or a critical connection. Fine for fitting covers, trim etc. I usually substitute Nylock where a lockwasher was originally used.

I also spray everything with NevrSieze. It makes disassembly a lot easier, even a decade later.

Asian Chrome varies, as you would expect

yes to anti-seize, unless threadlock is specified

like SS, there are many grades…the best fastener I ever come across are Caterpillar dark grey SS Torx head, used them for years as manifold downpipe bolts on a big 4wd, with nickel anti-seize, they looked brand new, and never came loose unless you easily undid them…not available to public

spent $400 on (non-structural) SS fasteners on my CCKW-353 now sold

Having spent decades working on heavy equipment- I agree with what Andrew said x2!

Anti-seize, always: I would not use any SS fasteners on any suspension component, unless I was 100% sure they were aviation grade-spec.

Chrome bolts, never, unless they has been treated for the hydrogen embrittlement chroming imparts.

A small bit related to Jaguars…

The chrome were going to be used on the GTO a/c brackets which will not undergo high stress, just look pretty!

Goat is in the shop undergoing

some serious bodywork. I will prolly have Stan do a bit of welding on my MK2.

NEVER leave a car under tarps as bad things happen!!

Stan is an independent guy who only works on GTO’s and charges $65 an hour which is an incredible rate.

Indeed: tarps are moisture traps. If left indoors, you are better off with no tarp!

Check the tensile strength on bolts in a McMaster-Carr catalog, its listed.

They usually won’t pass a tech inspection if you race as their strength is less, especially on critical suspension and steering components.

Plating has its own issues, just like on wire wheels with embrittlement.

Not to crazy with some of the stainless being sold. Seems to be quite an elastic standard with regards to strength depending on country of origin. Either that or their QC is sorely lacking.

When I served as Chief of Tech, forthe local chapter of SCCA, I ticked off more folks than you could believe, for using ungraded SS fasteners, or Gr. 5 where 8 should have been…or vice versa!

I’ve wondered about this. Grade 5 might deform but is less likely to break than Grade 8? Ditto for Grade 2 versus Grade 5?

Let’s consult the experts!!

His statements on fatigue are not quite right. Engineers use a technique to calculate the fatigue life of connections they design. The more fatigue cycles a part is exposed to the less stress it can sustain. It’s a balancing act.
With some steels if you can restrict the stress to below what is called the “endurance limit” then the part will not fail in fatigue. This can be a useful feature but items designed with this philosophy would never leave the ground…
The real Achilles heel of the threaded fastener is unfortunately the thread. The cut shape creates stress concentrations that can cause the connection to fail.
Rolled threads are better…but threaded connections are difficult to get right!!

Never understood the racer calling stainless an upgrade in light of its lesser tensile strength?

I gave this some thought when I prepared threaded rods for compressing front springs a while ago. I wondered if Acme, coarse, or fine threads would be better. One time when I was visiting my machine shop I raised the question during a coffee break. Everyone agreed that threaded fasteners always fail (in tension or in shear) before the threads strip. Fine threads are better because, in effect, they allow a larger (minor) diameter for the unthreaded inner part of the bolt for a given outside (major) diameter. This increases the effective cross-sectional area and strength.

The above is true only for adequate thread engagement length, which they calculate when necessary. If one uses a standard nut with the same grade as the bolt (instead of a tapped hole), the calculation was done a century ago–it is thick enough so that adequate engagement is guaranteed–the bolt will fail before the threads. When the bolt engages a tapped hole, the engagement length depends on the material. For aluminum, as we all know, course threads are better too.

IMHO as always.

Yes. The threads are fine for normal loads and were “blacksmithed” to be so … from early failures… but the Achilles heel I am talking about is fatigue. Your spring compressors will never get into fatigue territory. Engineers start worrying about the one to two hundred thousand cycles mark…so cylinder head fasteners, big end fasteners etc etc…
This is where stress concentrations start to wreak havoc… and the cut thread is a biggie.