Date: Fri, 8 Jul 2011 11:28:31 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: [Friday] Bolts -- Rockwell hardness translate to grade?
In-Reply-To: <1310098443.12454.65.camel@TheJackUbuntuNetbook>
Content-Type: text/plain; charset="UTF-8"
As bolts usually work in tension the ratings mostly deal with tensile strength. While there may be some correlation, the hardness of a material is not directly related to strength, especially in cases where the hardness is only at the surface. Since he gave you hardness rating with a "B" this is a Brinell, not Rockwell rating. Steel can be hardened to the point it can be brittle.
That shear bolt was a custom part, with only thread near the end or a hole for clip/pin. The fact that it is bent indicates the jack was at least once overloaded.
I would start with a standard grade 2 bolt, long enough to have the shoulder pass through the working parts and cut the excess thread off. You may want to use a locknut to keep it in place as you can't just tighten it down.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Rocket J Squirrel
Sent: Friday, July 08, 2011 12:14 AM
To: vanagon@GERRY.VANAGON.COM
Subject: [Friday] Bolts -- Rockwell hardness translate to grade?
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)
