I guess I didn't explain that the shear bolt is supposed to shear under
great stress, before the rest of the jack fails, so going to super-hard
defeats this safety feature.

The point of my question which might have been so long-winded that the
actual sentence ending with a question mark is whether I came close to
translating Rockwell hardness to bolt grade.

On Fri, 2011-07-08 at 00:37 -0400, Kim Brennan wrote:

> www.mcmaster.com
>
> Get the right stuff. If you choose the military grade stainless, it will most likely be more than enough.
>
>
> On Jul 8, 2011, at 12:14 AM, Rocket J Squirrel wrote:
>
> > Hi all (jumping the gun a bit on that Friday thing  . . . )
> >
> > I bought a Hi Lift jack from Al "Pensioner" Knoll earlier this year.
> > It's a vintage piece. Very cool.
> >
> > I just went to refresh the critical parts on the jack with ones from Hi
> > Lift's jack rebuild kit, but the shear bolt and the climbing pins in the
> > kit don't fit.
> >
> > Puzzled, I contacted Hi Lift and described what I was looking at and the
> > fellow there said that the jack was made prior to 1960 (!) and they
> > don't have parts for it.
> >
> > While the original climbing pins are in good shape, the original shear
> > bolt is bent a bit. Needs replacing. I asked Hi Lift what grade of bolt
> > I could use there and the nice man wrote back to say:
> >
> > "I’ve been a couple of days trying to get you an answer, but with little
> > success.  Our shear bolts are specially made and heat treated for us.
> > The Rockwell hardness scale on these bolts ranges from B85-95, with most
> > testing to B89-90.  I’ve been trying to find out what bolt that compares
> > to but have failed to find any comparison."
> >
> > So I looked at some charts this morning and, if using tensile strength
> > is any indication, this Rockwell hardness translates to something like
> > 88,000 psi. Grade 2 bolts come in at around 74,000 and Grade 3 (a
> > rarity, I think) are more like 110,000. It's a 1/4'' bolt.
> >
> > Did I count on my fingers and toes good enough?
> >
> > The fellow went on to add that,
> >
> > "I know my dad would break his shear bolt and just stick another bolt
> > into it, but that is not a recommended safe practice.  I wish I could
> > just send you a shear bolt, but we’ve checked and don’t have any laying
> > around after all of these years."
> >
> > Fair enough.
> >
> > So I got four choices here: re-assemble the jack and sell it on
> > craigslist with a caveat and buy a new jack, re-assemble this one with
> > the deformed shear bolt and see if it holds when I need it (not so
> > smart), or bang in some Grade 1 or 2 bolt* from the hardware store
> > (unknown degree of smartness).
> >
> > Ideas?
> >
> > =============
> > * There does not seem to be any way to determine whether a bolt is Grade
> > 1 or 2, as neither have marks on the head. So what's my Ace Hardware
> > store gonna stock? It is a mystery!
> >
> > --
> > Rocky J Squirrel (Jack Elliott)
>