amace@unix2.nysed.gov wrote:
>
> On Fri, 10 Jan 1997, Tony Robinson wrote:
>
> > Trot right down to your local parts store and get grade 8 sae fine
> > thread bolts.
>
> Tony, when I put together my 1147 Spitfire race motor last spring after
> an overhaul, I checked with a local mechanic (top-notch, and an
> engine-builder and former stock car racer of some repute) about rod
> bolts, torque, lock-tite-style compounds, etc. He told me that the design
> of a rod bolt allows a certain bit of stretch and/or something else that
> keeps it in place without lock tabs or washers, and that those were not
> necessary, nor was any sort of lock-tite.
>
> Would a Grade 8 bolt feature those same properties, unless specifically
> desinged for use as a rod bolt? Just curious....
>
> --Andy
>
Andy,
Some years back, I did som research on British "auto grade" bolts.
I couldn't begin to tell you where I found the information, but a
Whitworth/auto grade bolt as used in the body and chasis is the
equivilent of a S.A.E. grade 5 which is what you normally get in the
blister packs at say K-Mart or Wal-Mart.
Used to be the practice of anodizing grade 8 bolts was common in the
UK, In the US, grade 8 is annealed a yellow tint, to distinguish between
metric grade 8, which is anodized black.
I think what your friend was referring to was tinsel strength.
That is the rigidity of the combined effects of torque on both
stretching and twisting in application just before breaking.
They key to holding a bolt in place is in fact the tinsel strength.
It is based on the assumption that if the bolt is torqued to spec
then the amount of "stretch" will provide a given amount of springiness
to keep the bolt from loosening.
The best bolts that money can buy would be assumed to be stainless
steel. BUT that is not true.
There are varying grades of stainless as well, some quite soft.
The very best that can be bought are "aircraft grade" at least as far
as I know. I think these are rated grade 10.
Now, I am not a Metalurgical specialist by any means.
I do know however, that the torque specification is based on the
diameter of the bolt shank and head and NOT the application.
American auto makers use a "peened" nut for securing rod caps to studs.
This in effect "ovals" the nut.
Lock-tite is great for its purpose, but, I think it was never used
on rods and mains because it tends to get super hard, even the lower
grades and, can take heat to remove. We all know that heating a rod or
main bolt is an absolute no-no.
Now, if you are building a U.S. engine that uses studs on the rods and
you want to be sure the studs will stay in, then I say go for the
Lock-Tite.
Sounds like I know a whole lot, but I really don't.
This is all just a matter of preference. As you know, we tend to pick
up things over the years and sometimes we think we know it all but,
someone will come along and and in effect, tell us we are full of "IT"
Take care,
TonyR
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