Collets for coupling rotary actuators to valves are disclosed. An example collet includes a first plurality of flexible members configured to be coupled to an elongated member and each having a first inner surface and a first outer surface. The first inner surface and the first outer surface define a first cross-sectional shape. The example collet further includes a second plurality of flexible members configured to be coupled to the elongated member and each having a second inner surface and a second outer surface. The second inner surface and the second outer surface define a second cross-sectional shape that is different from the first cross-sectional shape of the first plurality of flexible members. The first and the second outer surfaces are to engage a third inner surface of an opening of a lever that is configured to cause the first and the second plurality of flexible members to be displaced toward an axis of the elongated member to cause the first and the second inner surfaces to engage one or more surfaces of the rectangular shaft.