Fracture mechanics theory tells us that most fracture failures originate at highly stressed surfaces in tension. Surfaces loaded in compression do not tend to crack. That’s why surface pre-compression processes like shot peening or fillet rolling are so effective at improving fatigue life. Nitriding does the same thing.

Another important factor in pin bending stress besides Kt (stress concentration) is R (magnitude of load reversal). Judicious application of counterweights can reduce peak bending across the main pins.