Locking assembly for rotatable components

A starter assembly for a gas turbine engine comprising:

• a rotor shaft extending along a centerline axis, the rotor shaft defining a counterbore including a first portion having a greater diameter than a second portion;
• a turbine rotor rotatable with the rotor shaft;
• an epicyclic gear system including a sun gear, a plurality of intermediate gears and a ring gear, wherein the sun gear is mounted on an outer diameter of the rotor shaft, the plurality of intermediate gears mesh with the sun gear and the ring gear, and the epicyclic gear system interconnects the rotor shaft and an output shaft;
• a bearing assembly received on the rotor shaft axially between the sun gear and the turbine rotor relative to the centerline axis;
• a lock nut threadedly engaged with the outer diameter of the rotor shaft;
• and
• a retainer including a step portion extending from a head portion and including a projection portion extending from the step portion, wherein the step portion is dimensioned to establish an interference fit with the rotor shaft along the first portion of the counterbore, and the projection portion is threadedly engaged with the rotor shaft along the second portion of the counterbore such that the lock nut is biased against an axial end face of the sun gear.

A method of assembly for coupling together components of a starter assembly for a gas turbine engine comprising:

• mounting a gear on an outer diameter of a rotor shaft, the rotor shaft defining an inner bore extending from an axial end of the rotor shaft;
• fastening a lock nut onto the outer diameter of the rotor shaft such that the lock nut abuts against an axial end face of the gear;
• and
• fastening a retainer to the rotor shaft to bias the lock nut against the axial end face of the gear, including threadedly engaging a projection portion of the retainer in the inner bore such that a step portion of the retainer is moved along a centerline axis of the rotor shaft to establish an interference fit with the rotor shaft along the inner bore.