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Date:         Fri, 8 Jul 2011 08:30:25 -0700
Reply-To:     Rocket J Squirrel <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Rocket J Squirrel <camping.elliott@GMAIL.COM>
Subject:      Re: [Friday] Bolts -- Rockwell hardness translate to grade?
Comments: To: Jim Arnott <jrasite@eoni.com>
In-Reply-To:  <35383B48F8304B3991B75309CB8DF24D@JimArnottPC>
Content-Type: text/plain; charset="UTF-8"

Hey there Jim,

I appreciate the answer but it feels as though you are lecturing me. Maybe I'm misreading it.

On Fri, 2011-07-08 at 07:50 -0700, Jim Arnott wrote:

> Hey Rocky, > > You asked a question and got a precise answer from the manufacturer: "Our > shear bolts are specially made and heat treated for us." He then went > further and gave you the precise specifications for said bolt: "The Rockwell > hardness scale on these bolts ranges from B85-95, with most testing to > B89-90." You then looked up the tensile strength for a steel bolt with a > Rockwell of B85-95. (80-100kpsi) and you found that no standard bolt that > will suffice. This surprises you?

Did I express surprise?

As a manufacturer of consumer products for over 25 years I am well aware that off-the-shelf parts often don't meet the specs I'm seeing so we have them made.

I was not surprised. What I was hoping to find from the list here is whether the hardness he was able to provide could be translated into bolt grade. Just trying to expand my knowledge a bit, but mainly hoping to get a sense of how special their shear bolt is so I could determine the practicality of using an off-the-shelf part, because if I can't then I have to toss the jack.

> Having worked in aerospace heat-treat for > a few years, I can tell you that if there is an off-the-shelf material that > will do the job, we do not select a different material just so we can > process it. Shear bolts are the fuses of the mechanical world. You want them > to break so other more critical parts don't.

Yup yup yup. I get it, I get it. But sometimes a manufacturer will decide to source everything overseas and the engineering department will write out a full spec for the part for CYA purposes. It might well be that an off-the-shelf part will work, too, but then you don't have as much control over the QC. BTDT.

> > Hardware store bolts? Go to the fastener store. You know the one.... They > will know what you're talking about. Hardware store? They know it's a > "bolt."

Of course. Again, I feel lectured. I was starting at finding simple solutions, such as a suitable bolt being easily found at the local store. It could broaden from there, but let's face it: a new Hi Lift jack is less than $60 so at some point it's not worth it.

> > That being said, It's a 'shear' bolt. The tensile strength is not the only > spec you should be looking at here. > <http://www.ami.ac.uk/courses/topics/0123_mpm/index.html> If you want to > replace it right, use a shear bolt.

Love to. Don't have any more spec than thread size, length, and the hardness of the mfgr's bolt.

> Again, the fastener store may be able to > help. Otherwise, you'll need to contact an aircraft bolt supplier. > <http://www.aircraftspruce.com/menus/ha/bolts.html> as they actually KNOW > the specifications of their hardware.

I expect they do. The question here is whether the Rockwell hardness of the bolt is sufficient information to determine a replacement bolt's specs.

Thanks, Jim. Sorry for coming across all testy and disagreeable. I get irritated when I ask a question about a bolt and then my mailbox fills up with people telling me how stupid it is to get under a van supported by only a jack, something I didn't say I was going to do or would ever do.

I probably would have been better off just saying that I need to replace a discontinued shear bolt that has a Rockwell hardness of 90, and whether this can be translated into bolt grade.

Cripes. Wasn't looking to get upbraided for my question.


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