MAIN SPINDLE DEVICE

PROBLEM TO BE SOLVED: To provide a main spindle device which can excellently prevent the damage caused by a collision force from the radial direction and the axial direction without damaging a bolt, etc. SOLUTION: In the main spindle device 10, a radial clearance Cr between the inside peripheral surface of a fixed shock absorbing ring 25 and the outside peripheral surface of a rotary shock absorbing ring 27 is set to be larger than the deflection σrn of a rotary spindle 11 when a radial cutting force Frn is applied thereto, and to be smaller than the deflection σrc of the rotary spindle 11 when a radial collision force Frc is applied thereto, and an axial clearance Ca between the front end surface of the fixed shock absorbing ring 25 and the rear end surface of the rotary shock absorbing ring 27 is set to be larger than the axial displacement σan of the rotary spindle 11 caused by the deflection of a rolling bearing 13 when an axial cutting force Fan is applied thereto, and to be smaller than the axial displacement σac of the rotary spindle 11 caused by the deflection of the rolling bearing 13 when an axial collision force Fac is applied thereto. COPYRIGHT: (C)2007,JPO&INPIT