| 摘要 |
PROBLEM TO BE SOLVED: To enhance working accuracy by preventing a draw bar from rattling and a main spindle from vibrating while the main spindle is rotating. SOLUTION: This main spindle device for machine tool is provided with a hollow main spindle 1 capable of being attached with a tool at the front end thereof and a draw bar 6 for attaching and detaching a tool which is coaxially disposed inside the main spindle 1. A bush 12 having a thin wall part 12b capable of elastic deformation in the radial direction is fitted in a covering manner around the rear end part of the draw bar 6. The draw bar 6 is formed with a plurality of screw holes 14 extending forwardly from the rear end side thereof so as to be spaced equally in a circumferential direction and pressure screws 15 are screwed into the respective screw holes 14. The draw bar 6 is formed with through holes 16 which extend inwardly in a radial direction from the circumferencial surface of the draw bar and whose front ends face the screw holes 14 and pressure pieces 17 are fitted onto the inside of the respective through holes 16 so as to move in the radial direction of the draw bar 6. The pressing pieces 17 are moved outwardly in a radial direction by the pressure screws 15. As a result, the thin-wall part 12b of the bush 12 is subjected to elastic deformation outwardly in a radial direction by the pressing pieces 17, thereby being pressed against the inner-periphery surface of the main spindle 1.
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