| 摘要 |
PURPOSE: A head drum assembly is provided to avoid damage on the surface of a rotary shaft generated in assembling of a preloaded boss and the rotary shaft while easily assembling the components. CONSTITUTION: A head drum assembly(20) is installed on a drum base(10). A preloaded boss(30) having a protrusion(33) is inserted to the lower end of a rotary shaft(21) to give a preload to a lower ball bearing(B). The preloaded boss has a spiral groove(31) formed in a certain depth and a recessed groove(34) communicating to the spiral groove while having a wider width than the spiral groove. The recessed groove is formed lengthwise on the inner face of the preloaded boss. A screw(32) is combined via the spiral groove of the preloaded boss for fixing the preloaded boss to the rotary shaft. Herein, the burr generated while forming the spiral groove on the preloaded boss does not contact with the rotary shaft by the recessed groove for preventing damage on the surface of the rotary shaft. Moreover, the preloaded boss is easily assembled and disassembled by the recessed groove.
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