| 摘要 |
PURPOSE:To reduce the frictional coefficient between a tape type recording medium and a head drum by fitting a metallic sleeve at the outer circumference part of a molded matter forming a center part of the drum and winding the tape type recording medium round the outer circumferential surface of said sleeve. CONSTITUTION:A composite molded matter 9 set at the center of a head drum contains a boss 1 at its center part and the boss 11 has a through hole 12 through which a support shaft is put. A sleeve 10 made of an aluminum alloy is fitted at the outer circumference part 13 of the matter 9. Both the sleeve 10 and the part 13 are unified together by press fitting or adhesion. Thus, the outer circumferential surface of the sleeve 10 is cut with high precision on the basis of the hole 12 of the boss 11 because the sleeve 10 is joined to the part 113 of the matter 9. Then, the prescribed dimensional accuracy is secured together with the prescribed form accuracy and the prescribed surface roughness. As a result, the rubbing performance is improved between the head drum and a magnetic tape.
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