Grade 5 vs. Grade 8 Bolts...Which one to get?

[Thai]

While researching for my sliders, I found this very educational article on RockCrawler.com:

http://www.rockcrawler.com/techreports/fasteners/index.asp

Very interesting read. Hopefully, this will help you pick the right kind of bolts for your rig or accessories (winches, bumpers).

Basically, Grade 8 bolts are stronger than Grade 5 in every measurable way. Grade 8 bolts are NOT brittle.

Here is the conclusion at the end of the article:

Getting back to the original question,

 

[Thai]

Interesting tidbit: a bolt will break off (shearing force) before it strips (tension force).

 

[Good Times]

Good article! A good rule of thumb is to always use Grade 8 minimum for all aftermarket parts or higher. Remember Safety First.

 

[peter78]

Interesting article. About 6 years ago I bought 1000 metric nuts and bolts from Harbor Frieght. They came in little bins and they are grade 5. I never knew what grade 5 meant.

It is amazing how many times I have used the bolts. When trim falls off my car, I match the bolt that fell off. I use them on the boat, on my shed and many other ietms around the house. These are of course cheap bolts not to be used for heavy duty things like mods on your SUV.

 

[brick privy]

scaned the article. appears this guy was talking about larger diameter bolts like the ones on winches, bumpers, etc..

actually, the diferance between grade 5 and grade 8 is that the grade 8 is hardened. the hardening process increases the bolts tensile strength, most importantly it hardens the threads keeping them from striping out. the problem is that the hardening only goes so deep into the bolt and it DOES make the surface more brittle. so if you're using a small diameter bolt in a shear situation it may break before it bends.

 

[M3_962]

Here some info from someone I trust:

Q: replace 10.9 hardware with 12.9?

A: Not too good to cycle a 12.9 bolt.
Double Shear, Yes. Single shear, NO
But they never break anyway, except on airplanes

 

[Koz]

STAINLESS!

Koz

 

[brick privy]

stainless is brittle all the way through because of the chromium content. stainless will snap like a razor blade. don't use chrome plate either, the chroming process can make bolts brittle too.

 

[Koz]

stainless is brittle all the way through because of the chromium content. stainless will snap like a razor blade. don't use chrome plate either, the chroming process can make bolts brittle too.

Just recently there has begun to be a demand for high grade stainless hardware. Not all suppliers are aware of or carry it. Also it is approx 3 times the cost. This is grade 410 stainless, which is equaled to grade 8 steel (150K lb tensile strength).

Koz