Date: Fri, 8 Jul 2011 07:50:37 -0700
Reply-To: Jim Arnott <jrasite@EONI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jim Arnott <jrasite@EONI.COM>
Subject: Re: [Friday] Bolts -- Rockwell hardness translate to grade?
In-Reply-To: <1310098443.12454.65.camel@TheJackUbuntuNetbook>
Content-Type: text/plain; format=flowed; charset="UTF-8"; reply-type=original
-----Original Message-----
From: Rocket J Squirrel
Sent: Thursday, July 07, 2011 9:14 PM
To: vanagon@GERRY.VANAGON.COM
Subject: [VANAGON] [Friday] Bolts -- Rockwell hardness translate to grade?
"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."
=============
* 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!
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? 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.
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."
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. 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.
Regards,
Jim
