Patent ID: 8714893

Claim:
A tool holder, comprising: a tool holder main body having a rear hole, an intermediate hole, a collet holding hole, and a boundary wall surface, said rear hole extending forward from a rear end of said tool holder main body along an axis, said intermediate hole having an inner diameter larger than an inner diameter of said rear hole, connecting to a forward end of said rear hole and extending forward along said axis, wherein said collet holding hole comprises a tapered hole and connects to a forward end of said intermediate hole, extends to a front end of said tool holder main body along said axis, and has an inner diameter increasing toward said front end, and wherein said boundary wall surface is a flat annular boundary wall surface on a radial plane located along a boundary between said rear hole and said intermediate hole and faces forward toward said front end; a tapered collet detachably inserted in said collet holding hole, having a tool insertion hole formed in a front end region of said collet, having a tapered outer wall that is slotted with slots, and being formed so that an outer diameter of an outer peripheral surface of said front end region increases toward said front end; a drawing screw positioned in said intermediate hole, and having a head and a screw shaft, said head having an outer diameter larger than said inner diameter of said rear hole, a rear end face of said head facing said boundary wall surface, said screw shaft having an outer diameter smaller than said outer diameter of said head, said drawing screw being inserted into said intermediate hole through said collet holding hole before insertion of said tapered collet, and a front end region of said screw shaft being screwed in a rear end of said collet, wherein said flat annular boundary wall surface is positioned and configured to contactingly receive said rear end face of said head of said drawing screw so as to limit movement of said drawing screw toward said rear end; and a stopper member positioned in an annular space between an outer peripheral surface of said screw shaft of said drawing screw and an inner peripheral surface of said intermediate hole, and facing a front end face of said head of said drawing screw, for limiting movement of said head toward said front end; wherein said drawing screw, said stopper member, said tapered collet and said tapered hole are arranged, configured and cooperate with one another so that when said drawing screw is screwed into said collet, said drawing screw moves tightly against said stopper member and then said drawing screw draws said tapered collet farther into said tapered hole toward said rear end whereby said tapered hole squeezes said tapered collet so that said slots are squeezed and an inner diameter of said tool insertion hole shrinks radially inwardly.