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Re: [Shop-talk] Another Snow Blower Question

To: Steve Shipley <shiples@comcast.net>
Subject: Re: [Shop-talk] Another Snow Blower Question
From: Michael Porter <mdporter@dfn.com>
Date: Tue, 21 Dec 2010 21:55:31 -0700
On 12/21/2010 9:34 PM, Steve Shipley wrote:
>
> I've been under the impression  that Grade 5 bolts are rated for
> tension, not for shear.  And certainly not intended to be bent.


Umm, just for drill, all grades have shear ratings.  Shear strength is 
derived mathematically from tensile strength tests (nominally, for 
engineering purposes, I think it's something around 65% of tensile).  
So, if tensile yield is XXXX, shear yield is 65% of that, and that's the 
figure used to determine if the bolt meets proof loads in shear.


No bolt is intended to be bent, but, many are subject to shear loads, 
too, so they have to be calculated for a given application.  I've seen 
3/4" GR8 bolts with u-sections bent into them from shear loads between 
two plates that someone didn't calculate properly and didn't anticipate 
the shear loads exceeding the ability of the clamping force to keep the 
plates in position (too much slop in the through holes combined with 
high shear forces causing the plates to slide back and forth and bang 
against the bolt shank).


Cheers.

-- 


Michael Porter
Roswell, NM


Never let anyone drive you crazy when you know it's within walking distance....
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