The applicants have already provided a main shaft device for machine tools comprising a tool holder removably fixed to the front of a main shaft driven for rotation, the tool holder comprising a holder main body, a chuck and a cutting tool stopper member. The main shaft supports the holder main body, and the chuck is mounted to the front of the holder main body. The cutting tool stopper member is mounted at the center of the holder main body, closely touching the rear end of a cutting tool clamped by the chuck, the stopper member controlling a backward displacement of the cutting tool. Cutting fluid mists fed inwardly into the rear of the main shaft through a mist passageway formed at the center of each of the cutting tool stopper member and the cutting tool spout from the front end surface of the cutting tool.
The cutting tool stopper member forms a straight cylindrical single member. The inner hole thereof is straight and has the same caliber in its optional longitudinal position.
Generally, the above-mentioned main shaft device has a marketable cutting tool mounted thereon. The caliber of a mist hole is suitably determined in accordance with an outer diameters or the length, of a cutting tool main body, the type of cutting tool or for the cutting tool maker's own peculiar reasons. Generally, the caliber of the mist hole has a size for passing a sufficient quantity of cutting fluid mists for various machining operations by the cutting tool.
In the above-mentioned main shaft device, the ability for feeding the cutting fluid mists from the main shaft to the cutting tool is made sufficient to carry out general various machining operations. Accordingly, cutting fluid mists arriving at the inside of the cutting tool after flowing out of the cutting tool stopper member spout from the front end surface of the cutting tool in a flow rate depending on the caliber or length of the mist passageway in the cutting tool.
Therefore, in many machining operations, too much cutting fluid mist comes to spout from the front end surface of the cutting tool, thereby wasting of cutting fluid mist and contaminating the machining environment with cutting fluid mist.
The present invention aims to provide a main shaft device for machine tools that can overcome the above problems.