Abstract: The invention includes an end cap that can be securely mounted to the end of a ceramic spool. The end cap comprises a locking plate adapted to fit into a groove in the ceramic spool. A plurality of angularly offset holes in the locking plate align with similar holes in the end cap. Screws or pins are placed in the holes and welded in place to prevent backing out or loosening. In use, the locking plate is secured by the pins, the groove and the inside surface of the end cap, the combination of which inhibits misalignment. Thermal cycling does not loosen the end cap, cause eccentric rotation or crack the ceramic spool.