Chuck for machine tools

A needle-roller type chuck for machine tools comprising:

• a chuck body having a longitudinal axis and a leading end portion;
• a chuck barrel integral with the leading end portion of said chuck body and extending axially therefrom, said chuck barrel having a leading end portion, an outer peripheral conically tapered surface and a plurality of holes circumferentially distributed about said axis and extending from the leading end of said chuck barrel toward said chuck body;
• a rotatable clamping ring positioned over said chuck barrel, said clamping ring having an inner conical surface extending in the axial direction of said chuck body and parallel with the outer peripheral surface of said chuck barrel;
• a needle roller assembly having a predetermined axial length, said assembly comprising a plurality of needle rollers positioned between said chuck barrel and said clamping ring in rotatable contact with the conically tapered surface of said chuck barrel and conical surface of said clamping ring;
• and
• the axial length of each of the plurality of holes corresponding substantially to the predetermined axial length of the needle roller assembly.