[hauss]

Originally Posted by olddog

When steel breaks it is usually a combination of hardness and places left by machining that cracks propagate from. The harder the steel, typically the more brittle. These types of steel takes a lot more care in designing a radius verses a sharp corner. Also all tooling marks left be machines need to be ground smooth. It's like scratching a piece of glass to control where it will break with very little pressure. I have worked with some hardened tool steels that in the hardened state nothing can machine them. The wear of the the parts are amazing and the are super strong (wont deflect at all), but drop it and it will shatter like glass.

This all said, I would suspect that when they machine the hole in the pin they are leaving sharp scratches on a microscopic level. I would inspect the next new pin under as much magnification as I could get access to. If I found any spots that a crack could start, I would polish them out.

The edges on the new one looked like someone cut the hole with a plasma cutter very rough you may be on to something