Tool holder

A tool holder comprising:

• a collet chuck body;
• a slotted taper collet to be fitted in a tapered hole formed in the front-end portion of said collet chunk body;
• a locknut which is screwed with a male screw portion formed on the outer circumference of the front-end portion of said collet chuck body and which chucks a cutting tool by inserting said taper collet into said tapered hole, wherein
• said taper collet has, at the front end of the cutting tool inserting side thereof, a reference end perpendicular to the axis line of the taper collet and a cylindrical nut engaging portion protruded from said reference end with its axis line aligned,
• said locknut has a collet supporting portion formed in a manner protruded in the center direction of the locknut so as to be opposed to said reference end and an insertion hole concentrically formed in the center of said collet supporting portion so as to allow an insertion of said nut engaging portion,
• said taper collet has a brim portion which is formed on the outer circumference of the front end of said nut engaging portion inserted through said insertion hole and which couples, by latching with the marginal rim of said insertion hole, said taper collet to said locknut so as to be relatively rotatable,
• a metal ring plate-like bearing washer is interposed between said reference end and said collet supporting portion opposed thereto, and
• to at least one surface of said bearing washer which comes into contact with said reference end and said collet supporting portion, surface treatment to reduce frictional resistance between both contact surfaces is applied.