Scope: Ground precision shaft with case-hardened wear surface, a 3.5mm-pin-verified diameter callout, and a 10:1 scaled detail isolating a sub-.020″ radius blend.
Approach: Case-hardened 8620 at RC 57-62 needs a documented case depth (.02″-.04″ here) or the heat-treater has no target to hit. The .690 diameter was specified with an explicit “3.5mm pin used for measurement” note, since a standard micrometer can’t seat reliably in that groove — removing the single most common inspection dispute on ground shafts.
Result: A drawing a heat-treat vendor and a CNC grinder can both work from without a phone call.
