A wedge 32 for a rotor 12 of an electric machine includes a circumferentially outer surface 34 defining a radial extent of the wedge 32 extending from a first axial end 42 of the wedge to a second axial end 44 of the wedge. A plurality of circumferentially-extending grooves 46 extend radially inwardly from the circumferentially outer surface to a groove depth. The plurality of grooves 46 are axially spaced along a wedge length between the first axial end 42 and the second axial end 44. The axial spacing between the grooves is greater than an axial width of each groove. An intermediate surface 70 between adjacent grooves has a same radial position as a first end surface between the first axial end and a first groove closest to the first axial end. Two planar side surfaces 38 circumferentially bound the circumferentially outer surface and extend radially inwardly from the cicumferential outer surface.