Tool holder

A tool holder which is mounted on a machine tool for holding a tool for machining a work piece, comprising:

• a tool mounting part connected to a spindle of the machine tool, the tool being mounted on the tool mounting part;
• and
• a support part fixed to a body side of the machine tool, the support part supporting the tool mounting part via a bearing so that the tool mounting part is rotatable, wherein
• the tool mounting part contains in its inside:
• a mist generating nozzle formed in a cylindrical shape in which an atomizing space is formed in its center so as to be opened forward, and in which an oil introducing passage communicating with a rear side portion of the atomizing space and a water introducing passage communicating with a front side portion of the atomizing space are formed;
• and a top nozzle disposed in a front side portion of the mist generating nozzle to abut on a rear end portion of the tool so as to communicate with an in-tool passage formed inside the tool,
• an oil supply passage which supplies oil to the oil introducing passage by carrier gas consisting of compressed air, and a water supply passage which supplies water to the water introducing passage are formed in the support part, and
• when the oil supplied via the oil supply passage and the oil introducing passage reaches the atomizing space, the oil is atomized by an air flow of the carrier gas consisting of the compressed air, the water supplied from the water supply passage and the water introducing passage is formed into a water drop in the atomizing space by an air flow of oil containing compressed air containing said atomized oil so as to generate a water drop with oil film in which the oil film is formed on a surface of the water drop, and the water drop with oil film is supplied to the work piece through the top nozzle and the in-tool passage.