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?
In-Reply-To: <35383B48F8304B3991B75309CB8DF24D@JimArnottPC>
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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.