| 摘要 |
PURPOSE:To prevent lowering of machining capacity when spindle is fed out by employing a multi-layer structure where a tube is fitted over the outer circumference of boring spindle and securing a member having high modulus of longitudinal elasticity to the outer circumference. CONSTITUTION:A boring spindle 2 is slidable axially in a hollow shaft 4, and a key 6 is engaged in a key groove 8. A tube 3 is fitted slidably against the spindle 2 and slightly movably each other over the outer circumference of the boring spindle 2. Since there is a proper frictional resistance between them, vibration is damped through frictional resistance against the tube 3 even if the boring spindle 2 vibrates during cutting work, and thereby machining capacity can be improved under the condition where the boring spindle 2 is fed out. When the tube 3 is made of material having high modulus of longitudinal elasticity, e.g. super hard material or some type of ceramic, and secured to the boring spindle 2, rigidity of the boring spindle 2 is improved resulting in improvement of cutting capacity.
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