pic: Stress plots related to broken output shaft

[artdutra04]

Originally Posted by M. Mellott

One option that comes to mind might be to use a tool that has radii in the bottom corners (or completely rounded on the bottom and cut your groove a few thousandths deeper) rather that sharp points. Sharp edges are stress concentrators, so the blends might remove some of the stress points.

Now, one might say a completely rounded groove bottom might also take away too much of the vertical side walls of the groove and defeat the primary purpose--holding a snap ring and supporting an axial load...but some snap rings have rounded cross-sections, so...

Personally, I'm a fan of just using Delrin spacers in the high torsion areas of shafts to transmit any axial loads to whatever is being used for shaft retention (stepped shafts, tapped ends with washer, snap rings, etc) at the non-torsionally-loaded ends of the shaft.