Method and appartus for retaining a tool in a tool holder with defined contact surfaces

Abstract

A plurality of friction rods each of which is positioned in a hole around the retaining bore with a portion of each of the plurality of friction rods partially protruding into the retaining bore for directly engaging the shank of the tool for holding the shank of the tool in the retaining bore at the defined contact surfaces.

We claim: 
     
         1 . A tool holder comprising:
 a first section adapted to be connected to a machining center;   a tool holding section for receiving and holding a shank of a tool therein, wherein the tool holding section comprises of   a solid body with an axis of rotation extending there through;   an outer diameter surface around the solid body;   a front face perpendicular to the axis of rotation;   a retaining bore centered on the axis of rotation and extending from the front face into the solid body for receiving and holding the shank of the tool therein; and   a plurality of defined contact surfaces each partially protruding in the retaining bore for directly engaging the shank of the tool for holding the shank of the tool in the retaining bore at the defined contact surfaces.   
     
     
         2 . The tool holder of  claim 1 , wherein the retaining bore is formed with the plurality of defined contact surfaces. 
     
     
         3 . The tool holder of  claim 1 , wherein the defined contact surfaces further comprise a plurality of friction rods equally spaced around the retaining bore wherein a surface of each of the plurality of friction rods is exposed and protrudes in the retaining bore to directly contact the shank of the tool for holding the shank of the tool in the retaining bore. 
     
     
         4 . The tool holder of  claim 3 , wherein the plurality of friction rods each comprise one chosen from a cemented carbide material, a ceramic material, and a hardened steel material. 
     
     
         5 . The tool holder of  claim 3 , and further comprising three friction rods equally spaced around the retaining bore and each with a surface exposed and protruding in the retaining bore for directly contacting the shank of the tool for holding the shank of the tool in the retaining bore. 
     
     
         6 . The tool holder of  claim 3 , further comprising a plurality of holes extending into the front face of the tool holding section around the retaining bore, wherein the plurality of friction rods are positioned in the corresponding plurality of holes. 
     
     
         7 . The tool holder of  claim 1 , and further comprising a space between a wall of the retaining bore and the shank of the tool created by engagement of the plurality of defined contact surfaces directly engaging the shank of the tool. 
     
     
         8 . The tool holder of  claim 7 , and further comprising a coolant hole extending into the retaining bore for providing coolant to the space between the wall of the retaining bore and the shank of the tool. 
     
     
         9 . The tool holder of  claim 7 , wherein the plurality of defined contact surfaces are formed integral with and as a single piece of material with the solid body, wherein the plurality of defined contact surfaces each partially protrude in the retaining bore for directly engaging the shank of the tool for holding the shank of the tool in the retaining bore at the defined contact surfaces. 
     
     
         10 . The tool holder of  claim 9 , and further comprising a plurality of depressions formed in the face of the solid body oriented around the bore and comprising between two depressions one of the plurality of defined contact surfaces. 
     
     
         11 . A method for creating a shrink-fit tool holder for retaining a shank of a tool, the method comprising:
 forming in a front face of a tool holding section centered on a rotational axis a retaining bore for holding the shank of the tool; and   forming in the front face of the tool holding section of the shrink-fit tool holder a plurality of defined contact surfaces each partially protruding in the retaining bore for directly engaging the shank of the tool for holding the shank of the tool in the retaining bore at the defined contact surfaces.   
     
     
         12 . The method for creating the shrink-fit tool holder of  claim 11 , further comprising forming a plurality of circumferentially spaced holes around the retaining bore each for receiving a friction rod of a plurality of friction rods. 
     
     
         13 . The method for creating the shrink-fit tool holder of  claim 12 , further comprising changing a relative diameter of the plurality of circumferentially spaced holes and the friction rods. 
     
     
         14 . The method for creating the shrink-fit tool holder of  claim 13 , further comprising inserting the plurality of friction rods into the corresponding plurality of circumferentially spaced holes. 
     
     
         15 . The method for creating the shrink-fit tool holder of  claim 14 , further comprising fixing the plurality of friction rods in the corresponding plurality of circumferentially spaced holes by allowing a relative diameter of the circumferentially spaced holes and the plurality of friction rods to equalize. 
     
     
         16 . The method for creating the shrink-fit tool holder of  claim 15 , further comprising inserting the shank of the tool into the retaining bore. 
     
     
         17 . The method for creating the shrink-fit tool holder of  claim 16 , wherein the step of inserting the shank of the tool into the retaining bore further comprises changing a relative diameter of the shank of the tool and the retaining bore. 
     
     
         18 . The method for creating the shrink-fit tool holder of  claim 11 , further comprising forming a plurality of depressions around the retaining bore wherein one of the plurality of defined contact surfaces is formed between a pair of plurality of depressions such that the plurality of defined contact surfaces are formed integral with and as a single piece of material with the tool holding section, and wherein the plurality of defined contact surfaces each partially protrude into the retaining bore for directly engaging the shank of the tool for holding the shank of the tool in the retaining bore at the defined contact surfaces. 
     
     
         19 . A tool holder comprising:
 a first section adapted to be connected to a machining center;   a tool holding section for receiving and holding a shank of a tool therein, wherein the tool holding section comprises of   a solid body with an axis of rotation extending there through;   an outer diameter surface around the solid body;   a front face perpendicular to the axis of rotation;   a retaining bore centered on the axis of rotation and extending from the front face into the solid body for receiving and holding the shank of the tool therein; and   a plurality of friction rods each of which is positioned in a hole around the retaining bore with a portion of each of the plurality of friction rods partially protruding into the retaining bore for directly engaging the shank of the tool for holding the shank of the tool in the retaining bore at the defined contact surfaces.   
     
     
         20 . The tool holder of  claim 19 , wherein the hole around the retaining bore for receiving the friction rod is formed in the front face of the solid body and extends into the solid body parallel to the axis of rotation, and into which the friction rod of the plurality of friction rods is fixed.