Patent ID: 8096737

Claim:
A spindle device of a machine tool comprising: a spindle head; a spindle which is rotatably supported by said spindle head and to which a tool holder is attachable; and a clamping mechanism clamping and unclamping the tool holder to and from said spindle, wherein: said clamping mechanism includes: a draw bar having a longitudinal axis and bringing an engaging claw into engagement with the tool holder or releasing the engagement; and a drive mechanism moving said draw bar in an unclamping direction; said draw bar has a draw bar-side suction hole penetrating through said draw bar in an axial direction and communicating with a holder-side suction hole formed in the tool holder; said draw bar includes: an engagement drive part moving the engaging claw to an engagement position with the tool holder; and a draw bar main body connected to the engagement drive part; the engagement drive part is inserted in the draw bar main body and detachably connected to an inner surface of the draw bar main body; and said drive mechanism has an inner pipe into which a rear end of said draw bar main body is inserted, and the spindle device further comprising a seal mechanism which is provided between said inner pipe and said draw bar main body and which has a seal member fixed to said inner pipe and slidably in contact with an outer peripheral surface of said draw bar main body.