Method of attaching a metal shaft to a ceramic shaft and product produced thereby

A method of attaching a metal shaft (10) to a ceramic shaft (12) having a first diameter (d1) is characterized by the following steps. A shaft portion (16) is formed on the ceramic shaft with a second diameter (d2) less than the first diameter. The shaft portion extends from a free end (18) thereof along a portion of the length of the ceramic shaft to a terminal end (20) thereof where the ceramic shaft has a raised portion (22) formed thereon having a third diameter (d3) less than the first diameter but greater than the second diameter. The free end of the shaft portion has threads (24) thereon. A circular shaped expansion sleeve (26) is placed on the shaft portion in an encircling relationship therewith, the expansion sleeve extending from the raised portion of the metal shaft to a location (28) adjacent a termination of the threads on the shaft portion. All of the members are cooled and then assembled with the metal shaft. The metal shaft is formed so as to have both a hollow interior portion (30) having a diameter slightly greater than the third diameter of the raised portion of the ceramic shaft and an internally threaded hollow portion (32). The assembly is carried out so that the threads of the ceramic shaft are mated with the threads of the metal shaft. The expansion sleeve is trapped in a volume defined by the shaft portion of the ceramic shaft, the hollow interior portion of the metal shaft, the raised portion of the ceramic shaft, and a closed end (34) of the hollow interior portion of the metal shaft.