Prevention of inner ring deformation and cracking due to over-tightening of set screws
One might think that fastening set screws tighter would prevent loosening. However, over-tightening of set screws leads to a heart-shaped deformation of the inner ring circumference, as shown in Fig. below.
At the same time, the inner ring becomes similarly deformed and the internal clearance gradually gets smaller, eventually leading to bearing failure. Thus, it is recommended that set screws be fastened at the appropriate torque.
To prevent the inner ring from cracking due to over-tightening of set screws, some models are induction-annealed.