PROBLEM TO BE SOLVED: To prevent the back-flow of cutting liquid in an air flow path while cleaning tapered holes and tools and preventing biting of tools.;SOLUTION: The spindle device 2 of a machine tool 1 performs cleaning of the tapered hole 6a and application of lubricating oil by discharging air to the tapered hole 6a at the tip of the spindle. The spindle device 2 comprises a hollow spindle 6, to a tapered hole 6a at the tip end of which a tool holder 13 is attached, and an air discharge hole 21 for discharging air from the tapered surface. In the spindle 6, a push rod 16 having a retractable cutting fluid flow path, a main air blow flow path 30 for supplying air containing misty lubricating oil to the air discharge hole 21 on the outer peripheral side of the push rod 16, and a seal piston 22 which is openable/closable the air communication passage 14c by moving forward and backward in an expanded diameter passage 14a of the main air blow flow passage 30 are comprised. During the time of clamping, the air communication passage 14c is closed by the seal piston 22 to prevent the back-flow of cutting fluid from the tapered hole.;SELECTED DRAWING: Figure 2;COPYRIGHT: (C)2019,JPO&INPIT
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