Patent ID: 8678724

Claim:
A tool holder for attaching a tool to a main shaft of a machine tool, wherein comprising: a shank portion provided on one end of said tool holder and gripped by said main shaft; a tool attachment portion provided on another end of said tool holder and having an insertion port into which said tool is inserted in a tip end surface thereof; a cover having a tubular wall that covers an outer periphery of said tool attachment portion and a bottom surface that covers said tip end surface of said tool attachment portion; a bearing provided between said tubular wall of said cover and said tool attachment portion; and a stopper that prevents said cover from co-rotating with said tool attachment portion, wherein a through hole penetrated by said tool and an ejection port disposed on a periphery of said through hole in order to eject a coolant toward said tool are provided in said bottom surface of said cover, a first flow passage through which said coolant supplied from said main shaft side flows is provided in an interior of said shank portion and said tool attachment portion such that said coolant is led between said tip end surface of said tool attachment portion and said bottom surface of said cover through said first flow passage, a second flow passage through which said coolant led between said tip end surface of said tool attachment portion and said bottom surface of said cover via said first flow passage flows toward said bearing is provided between said tubular wall of said cover and said tool attachment portion, and said bearing is lubricated and cooled by coolant supplied via said second flow passage, which forms a part of said coolant.