A rotor core for an induction motor. The rotor core includes a body that at least (i) extends axially from an outer surface of the body inward toward a central axis, (ii) extends from a first axial end to a second axial end, and (iii) defines a plurality of internal grooves. Further, each groove at least (iv) includes an opening at the outer surface of the body, (v) is defined by two opposing walls, (vi) extends from the first axial end to the second axial end, (vii) extends axially between the opening at the exterior surface and an inward end, and (viii) includes a body section. And wherein (ix) at least one wall of the opposing walls of the groove includes, in the body section of the groove, an extended segment forming a portion of increased breadth for the groove.