Method of attaching a metal shaft to a ceramic shaft and product thereof

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. A circular shaped metal lock nut (22) is placed on the shaft portion in an encircling relationship therewith. This lock nut has threads (24) on an outer facing surface thereof and a back end (26) which contacts the terminal end of the shaft portion. A circular shaped expansion sleeve (28) is placed on the shaft portion in an encircling relationship therewith, the expansion sleeve extending from the metal lock nut to the free end of the shaft portion. All of the members are cooled and then assembled with an adjustable metal plug (30) and the metal shaft formed so as to have both a hollow interior portion (34) and threads (36) formed on a free end (32) of the metal shaft. The assembly is carried out so that the threads of the lock nut are engaged with the threads of the metal shaft. The expansion sleeve is trapped in a volume defined by the shaft portion, the hollow interior portion of the metal shaft, the lock nut, and the adjustable metal plug. The plug is encircled by the hollow interior portion of the metal shaft and is located between the free end of the shaft portion and a closed end (38) of the hollow interior portion of the metal shaft.