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Date:         Thu, 7 Jul 2011 23:48:26 -0500
Reply-To:     Tom Hargrave <thargrav@HIWAAY.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Tom Hargrave <thargrav@HIWAAY.NET>
Subject:      Re: [Friday] Bolts -- Rockwell hardness translate to grade?
Comments: To: Kim Brennan <kimbrennan@MAC.COM>
In-Reply-To:  <D0228F63-92F2-41E2-876A-2547EE079B28@mac.com>
Content-Type: text/plain; charset="US-ASCII"

The shear bolts are designed to shear before something else breaks loose - this is a case where "better" isn't better and Military grade stainless is not the way to go.

Thanks, Tom Hargrave www.stir-plate.com www.towercooler.com www.kegkits.com

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Kim Brennan Sent: Thursday, July 07, 2011 11:37 PM To: vanagon@gerry.vanagon.com Subject: Re: [Friday] Bolts -- Rockwell hardness translate to grade?

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)

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