Dear Philip and Rob,
In his email today (copied below) Gary describes the kind of bolt failure
(in a 10mm x 50mm grade 8.8) that I experienced in my upper control arm.
The point to re-emphasize is that the break occurred precisely where the
threads begin (or is that where they end?), near the center of the bolt:
Half of the exposed surface showed corrosion and the remaining half was
still fresh.
Based on all that the experts here are advising about using a proper
fastener, I'll attempt a replacement of both metric bolts with a 7/16",
fine thread, grade 8, secured with several nuts.
Thanks to all for the important warnings!
Regards,
Teddy
Pgh PA
69 2000
PS Still 50s, rain to boot!
>Date: Wed, 26 May 1999 14:56:37 -0700
>From: Gary McCormick <svgkm@halley.ca.essd.northgrum.com>
>X-Accept-Language: en
>MIME-Version: 1.0
>To: Philip Erickson <philip.erickson@Agouron.COM>
>CC: ROADSTER <datsun-roadsters@autox.team.net>
>Subject: Re: bolts
>Sender: owner-datsun-roadsters@autox.team.net
>Precedence: bulk
>Reply-To: Gary McCormick <svgkm@halley.ca.essd.northgrum.com>
>
>Is this concerning the broken fastener in the front suspension? I lost
>track of the thread and have deleted the earlier messages... Anyway, I
>have seen the kind of failure that was described (corroded surface
>halfway across the diameter of the failure with fresh fracture face on
>the remainder) in personal experience.
>
>I heard a "pop!" while doing a U-turn to park in front of my place while
>driving my old PL521 ('70 Datsun pickup). Looked in the street and found
>what turned out to be one of the three fasteners which secured the
>steering box to the frame. I took it to work and had one of our
>specialists in the Materials Engineering department look at it. The
>verdict was stress-corrosion cracking - a failure that results from
>corrosion starting in a stress riser; for example, the sharp root of a
>thread. A surface crack starts and propagates through the section (how
>quickly depends upon how highly loaded the part is) until the remaining
>section is insufficient to take the sustained load or some momentary,
>higher load.
>
>This is another good reason to use a corrosion-inhibiting anti-sieze
>material when assembling threaded fasteners.
>
>Gary McCormick
>'70 2000
>San Jose, CA
>***********************************************
>
>Philip Erickson wrote:
>>
>> Teddy
>> I more correctly should have said ->
>> If you want bolts that are better as good as stock, get a shanked bolt
>> the correct length for your application in a grade designed for the
>> loading the fastener will see.
>> I still question if the bolt failed in shear.
>> I have seen grade 5 bolts streach and come loose.
>> Phil
>> --
>> Philip Erickson Phone: (619) 622-7963
>> Associate Scientist
>> Medicinal Chemistry FAX: (619) 678-8277
>> Agouron Pharmaceuticals, Inc.
>> 4215 Sorrento Valley Boulevard San Diego, CA 92121
>> _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
At 6:28 PM 5/26/99, Rob Robinson wrote:
>Me too!
>
>Rob
>
>> I still question if the bolt failed in shear.
>> I have seen grade 5 bolts streach and come loose.
>> Phil
>> --
>> Philip Erickson Phone: (619) 622-7963
>> Associate Scientist
>> Medicinal Chemistry FAX: (619) 678-8277
>> Agouron Pharmaceuticals, Inc.
>> 4215 Sorrento Valley Boulevard San Diego, CA 92121
>> _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
>>
>>
>>
|