Spindle unit and tool clamping device therein for machine tools

A tool-clamping device in a spindle unit for machine tools having a main spindle rotatably supported in a spindle head, the tool-clamping device comprising:

• an adapter disposed at a front end of the main spindle;
• a tool holder for holding a rotary tool;
• a short columnar lug integrally formed with the adapter;
• a cylindrical hole formed in the tool holder so as to be shrinkage-fitted on the columnar lug, wherein the adapter is made of a material having a coefficient of thermal expansion less than a coefficient of thermal expansion of a material of the tool holder;
• and
• rapid heating means and rapid cooling means for respectively heating and cooling the tool holder so as to enable a rotary tool to be replaceably held by a front end of the main spindle.

A spindle unit for machine tools comprising:

• a solid shaft main spindle formed of a rigid material;
• a spindle head rotatably supporting the main spindle;
• bearing means fashioned of a material which generates a small amount of heat;
• an adapter shrinkage-fitted on a front end of the main spindle and having a cylindrical hole therein coaxial to the main spindle;
• and
• a tool-clamping device including a tool holder having a columnar lug integrally formed thereon and adapted to be shrinkage-fitted in the cylindrical hole, wherein the tool holder is disengageable from the adapter so as to enable a replacement of the rotary tool with another rotary tool.

A tool clamping device in a spindle unit for machine tools having a main spindle rotatably supported in a spindle head, the tool clamping device comprising:

• an adapter disposed at the front end of the main spindle;
• a tool holder for holding a rotary tool;
• a short columnar lug integrally formed with the tool holder;
• a cylindrical hole formed in the adapter so as to be shrinkage-fitted on the columnar lug, wherein the tool holder is made of a material having a coefficient of thermal expansion less than a coefficient of thermal expansion of a material of the adapter;
• and
• rapid heating means and rapid cooling means for respectively heating and cooling the adapter so as to enable the rotary tool to be releasably held by the front end of the main spindle.