Spindle device of machine tool

A spindle device of a machine tool composing:

• a spindle (2);
• and
• a tool holder (18) fixed on a tip of the spindle mechanically detachably through clamping means (KR),
• wherein a mouthpiece member (23) in a fixed length is protrudently installed on a bottom face of a cavity “b” provided in a center of the tool holder (18) with a screw (24);
• wherein a gas-liquid passage (100), an atomizing means (101) and an in-spindle spray coolant passage (102) are provided in a center recess of a draw-bar of the clamping means (KR) in a spindle side,
• the atomizing means (101) comprising an atomizing nozzle (14) and a compressed air supplying valve (15),
• the atomizing nozzle (14) mixing and stirring coolant and compressed air supplied from a source outside of the spindle through the gas-liquid passage (100) to generate a spray coolant, and
• the compressed air supplying valve (15) being mounted to be displaced forward when pressure of the spray coolant spouted into the in-spindle spray coolant passage (102) in front of the atomizing nozzle falls, the compressed air supplying valve directly blowing the compressed air within a compressed air passage (100b) into the spray coolant;
• and
• wherein the in-spindle spray coolant passage (102) comprises an inner hole of the compressed, air supplying valve (15), and the compressed air supplying valve has an end that contacts on the rear end of the mouthpiece member (23) of the tool holder (18).