A RETAINER MEMBER (70) HAS A RETAINER PORTION (72, 73), A THROUGH HOLE (74), AND NON-CIRCULAR CROSS SECTION. A BEARING SECTION (55) IS DISPOSED ON AN OUTER PERIPHERY OF THE RETAINER PORTION (72, 73). THE THROUGH HOLE (74) HAS A CIRCULAR AXIAL CROSS SECTION AND AN INNER PERIPHERY, WHICH IS AXIALLY PENETRATED BY A NON-CIRCULAR PORTION (15B) OF A SPOOL SHAFT (15) FROM BACK TO FRONT. THE NON-CIRCULAR CROSS-SECTIONAL PORTION IS FORMED BY CUTTING OUT A FRONT END OF THE RETAINER PORTION (72, 73) BY MACHINING. THE NON-CIRCULAR CROSS-SECTIONAL PORTION HAS A NON-CIRCULAR AXIAL CROSS SECTION THAT ENGAGES THE NON-CIRCULAR PORTION (15B) OF THE SPOOL SHAFT (15). (FIG. 4)
