Mailing List flyrotary@lancaironline.net Message #43582
From: <wrjjrs@aol.com>
Subject: Re: [FlyRotary] Re: Safety wire
Date: Thu, 31 Jul 2008 12:10:15 -0400
To: <flyrotary@lancaironline.net>
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Dale,
I am a mechanical engineer by trade and do understand the difference, good call on your part. Truth is though that many socket head cap screws, aka allen screws, are case hardened, but in the head a good case hardening can result in through hardening. Semantics I know but either way it can be real tough on drills!
Bill Jepson


-----Original Message-----
From: Dale Rogers <dale.r@cox.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, 30 Jul 2008 5:26 pm
Subject: [FlyRotary] Re: Safety wire

Bill, 
 
"Case hardened" or "Through-hardened"? Either way, ditto on the cobalt drill bits, or for hole sizes larger than #20, maybe even "solid carbide". 
 
FWIW, I do case hardening. It is typically done to give a wear-resistant surface on a part that otherwise needs to be somewhat ductile underneath - which won't be the metal's strongest state. 
 
Dale R. 
 
wrjjrs@aol.com wrote: 
> Kelly, 
> That is true "except" that the better quality allen bolts, > Holo-Chrome, SPS, etc are case hardened. Be sure you get cobalt drills! 
> Bill Jepson 
> 
> 
 
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