Roller Latch Shaft Click on the title above each image to see the animated model of the fracture surface created with Helicon Focus and Helicon 3D Viewer. Right-click on each image below and select View Image to see it at full resolution in a new browser window.

Overall - 14X Stack: 0.010 inch increments

Closeup of oldest cracked area - 50X Stack: 0.001 inch increments.

Closeup of Central Area of Fracture - 50X Stack: 0.0005 inch increments.

I remember finding this thing - it's got a loosely fitting steel roller between two washer securely affixed to a splined shaft.  I forget what its exact function was.  It looks like a part of a door latch.  The roller is quite worn. The shaft failed in two stages.  The first stage formed an open crack which became quite rusty as seen in the upper row of images.  The second stage was low cycle fatigue without ongoing corrosion. It would be quite instructive to make a cross section of the shaft to see the microstructure of the steel and find out if there are other, unopened cracks.