Key pins and key bushings

[Ron Nossaman]

At 10:06 AM 5/27/99 -0400, you wrote:
>List:
>
>Let us get something curved here (as opposed to straight).
>
>Front key pins are oval, almost.  The two sides have a constant radii
>which means that, within certain limits, the interface area between
>the radii of both sides and a bushing remains constant, but relocated
>fore and aft.  
>
>This means that the contact surface will remain constant irrespective
>of the angle of the pin until the termination of the side radii.
>
>It is an old wives tale promulgated by lack of fore thought and
>undelineated parameters.
>
>Like any technical solution there are appropriate and inappropriate
>application approaches.
>
>In simpler words: You can turn key pins with no ill effect if done so
>thoughtfully and carefully.  We are technicians, be an intelligent
>one.
>
>		Newton



Hi Newton,

That's only true if the center of the curve radius corresponds to the center
of the pin, which isn't the case here. When you turn a front rail pin you
inevitably get a smaller contact surface than if the pin "flats" were
parallel to the bushings. The severity depends on how far you turn the pin.
Like you said, thoughtfully and carefully is the "key" (sorry). I don't like
to see this done with new bushings, but I don't see any real problem with it
as a means to get a little more mileage out of a set of bushings that's
coming up for replacement eventually.

 Ron