Shafts almost never break in the middle of a plain diameter. They break at a step, a keyway end, a groove, or a shoulder, because those are the places where the stress flow has to change direction and concentrates as it does. Which means the fillet radius at a diameter change is a fatigue-critical dimension, and it gets drawn as a small radius with a general tolerance more often than it deserves. The relationship is unforgiving in one direction. A generous radius spreads the stress and the shaft lives. A tight radius concentrates it, and the concentration factor climbs sharply as the radius shrinks relative to the diameter change. A shaft that is comfortably strong in plain section can be well outside its fatigue limit at a shoulder where somebody specified a 1mm radius because it looked tidy. Undercut relief grooves for grinding, sharp-cornered snap ring grooves, and keyway ends that stop abruptly all do the same thing. A Top Forging Manufacturer in India working on shafts should raise this at drawing review rather than forging the radius as drawn and waiting. Sharma Technocast produces forged shafts and rings with heat treatment, machining, and inspection in-house. For shaft and ring requirements, contact Sharma Technocast directly. contact@sharmatechnocast.com +91 9726666123