Last Dance at 1.2 Million Miles - 3216

[Hammerhead]

(08-08-2019 )Rawze Wrote:  Another related side-note: The wrist pins seem to be made of some seriously tough hardened steel,.. I mean seriously tough ... tool steel can't even hardly scratch one, it is that hardened, so one would think there is no way a wrist pin can fail and get sheered ... HOWEVER... They are only surface hardened, and are soft as butter in the center. I know this very well because I use old wrist pins for making things like collets, spacers, etc. (using my lathe). Once you get past that first 0.008" or so of that super-hardened coating, they are easy to machine.

Ah yes, the Hard Candy concept. Timken taper roller bearings (and I assume all others as well) use this same principal.
The idea is that the softer inner core can flex while the outter rigid shell maintains it's integrity. The theory is, that a hardened all the way through material source would shatter without a softer inner core to transfer the shock load to.