>
> For automotive applications where the bolt is actually going to be
> stressed, I like to use grade 5 when possible. If I can't find grade
> 5 in the size I want, then I will usually substitute grade 8. My
> reasoning behind this is that grade 2 may not be strong enough,
> whereas grade 8 will definitely be strong enough, but at the cost of
> being more brittle, which might allow a side load to snap it.
The gr5 can technically take more of a brute force impact due to "more
area under the curve" but the gr8 will take more force before it begins to
yeild. I use gr8 for everything vital on my equipment.
of course, don't go looking for gr5 and gr8 metrics - they'll be 10.2 and
12.8 as I recall. Unless it's 10.8 and 12.s. Those are the
nearly-analgus standards for the metric bolts.
> Anyhoo, grade 5 seems like a good compromise; its a lot stronger
> than grade 2, but not as brittle as grade 8.
but the grade 5 will still snap before the grade 8 deforms under a
constant load.
> I could be wrong,
> but I seem to think that grade 5 is the most common type of bolt
> used by the OEMs for stressed parts like suspension and driveline
> fasteners.
>
this I would agree with - except when they are 10.2s.
for way more than you want to know about metalurgy in a pretty
easy-to-understand format, check out this article that billavista wrote on
pirate 4x4
<http://www.pirate4x4.com/tech/billavista/PR-BV60/index1a.html>
-- +-- Mike Maskalans ---------------- Rochester, NY ----------+ | '98 Dakota CC, SAS on 40s '84 RamCharger 4x4, plow truck | | '02 Jetta TDI 5sp, daily '97 Intrepid, not on the road | +-------------------- <http://mike.tepidcola.com/trucks/> --+
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