Disk drive having a pivotal support structure capable of defining a unique position of a support member on a lower surface of a disk holding table

A disk driver having a pivotal support structure capable of defining a unique position of a support member has a disk holding table (10) and a support member (12) assembled to a lower surface thereof. The support member (12) is provided with an insertion hole (12b) formed at one end thereof. The insertion hole (12b) has a shape of an elongated hole extending along an imaginary line (L) between a center axis of the driving roller (15) and a center axis of a support pin (14). The elongated hole has a nonuniform width in a transversal direction perpendicular to the imaginary line (L). The width gradually reduces towards the driving roller (15) and is smaller and greater than a diameter of an engaging end (14a) of the support pin (14) at a closest portion closest to the driving roller (15) and at a remotest portion remotest from the driving roller (15), respectively. Following the movement of the support member (12) during rotation of the disk holding table (10) in a direction from the support pin (14) towards a driving roller (15), a circumferential wall defining the insertion hole (12b) is substantially brought into two-line contact (P1, P2) with a peripheral side wall of the engaging end (14a) of the support pin (14).