[TheForge] Timken Case Hardening was File Making

[David E. Smucker]

Mike,  To the best of my knowledge, Timken's process was a carbon based case 
hardening.  I worked a lot with Timken in the 90's on the development of a 
new bearing design for rolling mills.  Timken did the development work and 
we (Alcoa) did the mill design / field testing.  I got to see a lot of 
Timken's operations from the steel making to bearing manufacture and 
testing.  Interestingly Timken considered their case hardening process one 
of their area of special technical knowledge and would talk very little 
about it.  We could walk by the equipment, and they would say "this is where 
we case harden the bearing races" and then they would say "that is all we 
are going to say about it".  I understood, we had gauge, profile controls, 
and rolling lubrication that we would not talk about.  They would show 
etched cross sections of the races to show the depth of the case -- it was 
deep.  One thing you can do with very large roller bearings (56 inches OD 
for example) is regrind the inter and outer races and put over size rollers 
and get a second life out of the bearing.  We had Timken's largest bearings 
(about 80 inches OD) on our big plate mill at Davenport, IA and some of 
those bearings where rebuilt after about 20 years in service.

Dave Smucker
----- Original Message ----- 
From: "Mike Spencer" <mspencer at tallships.ca>
To: <theforge at mailman.qth.net>
Sent: Wednesday, March 19, 2008 6:41 PM
Subject: [TheForge] Re: File Making


>
>
> Dave Smucker wrote:
>
>> ...the very best roller bearings are case harden, very deep case, as
>> much as 0.060 deep and the core is a very tough alloy steel similar
>> to 4120.  (Timken, which in my experience with very large bearings
>> are the world's best.)  Same is true for high performance large gear
>> sets.
>
> So, Dave, is that carbon case?  Or nitriding?
>
> When I worked in a wire mill (Michelin) the capstan drums over which
> the wire passed in various continuous-process treatments had to have
> absolutely minimal wear since if one drum's diameter differed from
> another in the train or differed from one point to another along its
> surface, the wire speed wouldn't be consistent and there would be
> breaks, sags or snarls. So the the drums were machined to matching
> size, heated for hours (days? I forget) in a nitrogen atmosphere and
> then, if needed, finish ground to match with an optical comparator.
> They still didn't last forever but, according to the shop scuttlebut,
> they wouldn't have lasted a day without that treatment.
>
>
> - Mike
>
> -- 
> Michael Spencer                  Nova Scotia, Canada       .~.
>                                                           /V\
> mspencer at tallships.ca                                     /( )\
> http://home.tallships.ca/mspencer/                        ^^-^^
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