A disconnect mechanism having an engaged configuration and a disengaged configuration, the mechanism comprising: a hub attachable to a driven unit, said hub having an inward side and an opposing, user-accessible outward side, said hub having a threaded bore extending from said inward side to said outward side; an outer shaft having a bore extending axially therethrough, said outer shaft defining a threaded engagement with said bore of said hub to axially move said outer shaft between an outer-shaft seated position in which said outer shaft is relatively inwardly disposed with respect to said hub, and an outer-shaft withdrawn position in which said outer shaft is relatively outwardly disposed with respect to said hub; an inner shaft received within said outer shaft, said inner shaft axially movable with respect to said outer shaft between an inner-shaft seated position in which said inner shaft is relatively inwardly disposed with respect to said outer shaft, and an inner-shaft withdrawn position in which said inner shaft is relatively outwardly disposed with respect to said outer shaft; and a coupling gear axially fixed to said inner shaft, said coupling gear defining: an engaged position corresponding to the engaged configuration of the disconnect mechanism, said coupling gear in said engaged position when said outer shaft is in said outer-shaft seated position and said inner shaft is in said inner-shaft seated position, and a disengaged position corresponding to the disengaged configuration of the disconnect mechanism, said coupling gear in said disengaged position when said outer shaft is in said outer-shaft withdrawn position or said inner shaft is in said inner-shaft withdrawn position. a hub attachable to a driven unit, said hub having an inward side and an opposing, user-accessible outward side, said hub having a threaded bore extending from said inward side to said outward side; an outer shaft having a bore extending axially therethrough, said outer shaft defining a threaded engagement with said bore of said hub to axially move said outer shaft between an outer-shaft seated position in which said outer shaft is relatively inwardly disposed with respect to said hub, and an outer-shaft withdrawn position in which said outer shaft is relatively outwardly disposed with respect to said hub; an inner shaft received within said outer shaft, said inner shaft axially movable with respect to said outer shaft between an inner-shaft seated position in which said inner shaft is relatively inwardly disposed with respect to said outer shaft, and an inner-shaft withdrawn position in which said inner shaft is relatively outwardly disposed with respect to said outer shaft; and a coupling gear axially fixed to said inner shaft, said coupling gear defining: an engaged position corresponding to the engaged configuration of the disconnect mechanism, said coupling gear in said engaged position when said outer shaft is in said outer-shaft seated position and said inner shaft is in said inner-shaft seated position, and a disengaged position corresponding to the disengaged configuration of the disconnect mechanism, said coupling gear in said disengaged position when said outer shaft is in said outer-shaft withdrawn position or said inner shaft is in said inner-shaft withdrawn position. an engaged position corresponding to the engaged configuration of the disconnect mechanism, said coupling gear in said engaged position when said outer shaft is in said outer-shaft seated position and said inner shaft is in said inner-shaft seated position, and a disengaged position corresponding to the disengaged configuration of the disconnect mechanism, said coupling gear in said disengaged position when said outer shaft is in said outer-shaft withdrawn position or said inner shaft is in said inner-shaft withdrawn position.