Cutter holder assembly capable of reducing longitudinal assembling gap between cutter and collet

A cutter holder assembly comprising:

• a cutter holder;
• a collet disposed in the cutter holder and the collet including:
• a first end;
• a second end;
• a chamber formed in the collet and extending from the first end toward the second end of the collet;
• a mounting cavity formed in the second end of the collet and communicating with the chamber;
• and
• a positioning groove recessed in an internal peripheral surface of the chamber and the positioning groove having:
• a guiding channel extending from the first end toward the second end of the collet;
• and
• a limiting groove circumferentially extending along the internal peripheral surface of the chamber, communicating with the guiding channel, and spaced apart from the first end and the second end of the collet;
• a cutter set mounted in the collet and the cutter set including:
• a cutter body inserted into the chamber of the collet;
• and
• a positioning protrusion protruding from an external peripheral surface of the cutter body, extending into the positioning groove, and engaged with the limiting groove;
• and
• a resilience tightening set mounted in the mounting cavity of the collet and the resilience tightening set including:
• a mounting base connected to the mounting cavity via a threaded engagement;
• a spring room having an opening facing toward the cutter set, wherein the spring room is formed in the mounting base;
• a spring disposed in the spring room;
• a position ball movably disposed in the spring room, partially protruding out of the opening of the spring room, and pushed by the spring for pushing the cutter body toward the first end of the collet to keep the positioning protrusion tightly abutting against a surface of the limiting groove of the positioning groove adjacent to the first end of the collet;
• and
• a snap ring, which with respect to a longitudinal center axis of the mounting base, is located between the spring and the opening of the spring room, the snap ring interfacing with the position ball and having an inner diameter that is smaller than a ball diameter of the position ball.