The machine reel 511 is formed with a recess 559 for receiving a leader block fixed to a leading end of a magnetic tape. [0146] [II] Tape Thread Mechanism (FIGS. 27 to 29) [0147]FIG. 27 is a perspective view of the tape thread mechanism, and FIGS. 28 and 29 are a side view and a plan view of the tape threader, respectively.