DESCRIZIONE
An assembly for disconnecting portions of a downhole tubular string, such as a drill stem or drill string, and removing an upper portion of the tubular string from the lower stuck portion in a well, includes a connection between joints of two portions of the tubular string. The assembly includes two tubular members and an inner sleeve having two splines each with different angular pitches or teeth counts. The assembly may include a rotary shouldered threaded connection, wherein the two tubular portions are disconnectable at the rotary shouldered threaded connection in the assembly. The assembly may include a sleeve lock, a selective no-go for landing in a profile, and a selectively deployable unlocking and unblocking tool for activating the assembly. The assembly may include connectable cylindrical members other than downhole tubulars.