TOOL HOLDER GRIPPING DEVICE

PURPOSE:To improve the extent of clamping force by expanding the diameter of a clamping jaw part of a collet and moving it forcedly, while making a bull stud so as to be pulled out of the collet without fail, in a tool holder gripping device for a machine tool equipped with an automatic tool changer. CONSTITUTION:A recess part 23b is installed on the outer circumferential part of a hollow shaft 23 connected to a draw bar 22 of this gipping device, and in the rear end of a collet 24, there are provided with a vertical surface 26a, a first incline 26b and a second incline 26c respectively. This rear end of the collet 24 is made so as to be rockably inserted into the recess part 23b with an edge of the vertical surface 26a as the fulcrum. Likewise, on the outer circumferential part of the hollow shaft 23, there is provided with a ring pressing member 31 as movable in the axial direction. This pressing member 31 is pressed in the axial direction to the second incline 26c at the rear end of the collet 24 by a spring member 32 attached to the outer circumferential part of the hollow shaft 23 at the rear side of this pressing member 31.