A system comprises an instrument adapted to be manually supported and moved by a user. Said instrument includes a hand-held portion, a working portion movably coupled to said hand-held portion, a plurality of actuators operatively coupled to said working portion for moving said working portion in a plurality of degrees of freedom relative to said hand-held portion, and a tracking device attached to said hand-held portion for tracking said instrument. Said system further comprises a navigation system for determining a position of said working portion relative to a target volume of tissue to be remove, and a control system in communication with said actuators to control said actuators to move said working portion relative to said hand-held portion such that said working portion autonomously follows a path defined in said control system to remove material of the target volume while the user maintains said hand-held portion in a gross position relative to the target volume.
