Key pins and key bushings

[Ron Nossaman]

Hi again Newton,

My reply was , as usual, more simple minded than what I meant. True, the
contact *area* is the same up to about 20 degrees off straight, but the fore
and aft *position* of the contact changes as the pin is turned. That means
that the "adjustment" is more sensitive with worn bushings than with new
ones. You have to turn the pin further in new, straight sided, bushings to
take up the same slack. It would make no real functional difference in new
bushings if the pins are exactly straight or not, so you're right there
(though it seems kind of sloppy, and I know you wouldn't do it unless
threatened), but if there is any wear in the bushing, it makes a big
difference. With worn bushings, the contact area gets very small very
quickly with a few degrees of turn. That's what I meant by turning pins as a
means to milk a little more mileage out of a set of bushings. Incidently,
that 20 degrees (or so) turn only amounts to about 0.010" against parallel
sides. That kind of surprised me when I measured it just now.

If I screwed up my explanation of what I think I meant again, I've got a
drawing I can attach that makes it a little easier to visualize. 

Sorry about the incoherence.
 Ron