A composite tool unit, having opening and closure positions, for coupling a cutting member to a machine tool, comprising
- a tool shank having a longitudinal axis and a recess in the frontal face thereof, said recess including a peripheral wall with at least two axially spaced inner conical faces, the diameters of each of said inner conical faces being greatest at the ends thereof closest to the frontal face of said tool shank;
- a drawbar, connectable to a power drive of said machine tool, mounted within said tool shank and displaceable along the longitudinal axis thereof, said drawbar having a first annular radial outwardly projecting projection at a portion thereof located within said recess;
- a tool head for supporting said cutting member at one end, the other end of said tool head being longitudinally clampable against the frontal face of said tool shank, said tool head when clamped being centered about said longitudinal axis and non-rotatable with respect to said tool shank;
- a pulling shank attached to said tool head and projecting therefrom for insertion in the recess of said tool shank, said pulling shank including axially spaced second annular radial outwardly projecting projections for positioning within said recess, each of said projections having an external conical face on the side of said second projection facing said tool head, the diameters of each of said external conical faces being greatest at the ends thereof furthest from the frontal face of said tool shank;
- and
- a chuck having a plurality of individual clamping jaws extending parallel to the longitudinal axis of said tool shank and coaxial with said drawbar, said clamping jaws being disposed within said recess surrounding the first annular radial projection on said drawbar and the second annular radial projection on said pulling shank when said pulling shank is inserted in said recess, said clamping jaws having a first set of radially inwardly projecting projections at the end of said recess adjacent said drawbar and a second set of axially spaced inwardly projecting projections at the end of said recess adjacent said pulling shank, each of said second set of projections on said clamping jaws having an internal conical face on the side thereof furthest from said tool head corresponding to the external conical faces on the projections on said pulling shank, the diameters of each of the internal conical faces on said clamping jaws being greatest at the end thereof furthest from the frontal face of said tool shank, said clamping jaws further having axially spaced outer conical segments corresponding to the inner conical faces on the peripheral wall of said recess,
- whereby, when said unit is in its opening position said clamping jaws are resiliently expanded to permit withdrawal of said pulling shank from said recess;
- and when said unit is moved from its opening to its closure position said drawbar is displaced in the axial direction away from said tool head so that said first outwardly projecting projection on said drawbar contacts said first set of inwardly projecting projections on said clamping jaws to translate said clamping jaws in the axial direction parallel to said longitudinal axis away from said tool head, and the axially spaced outer conical segments on said clamping jaws slide on the axially spaced inner conical faces on the peripheral wall of said recess to move said clamping jaws radially inward until in the closure position the second set of inwardly projecting projections on said clamping jaws contact the flanks of the second outwardly projecting projection on said pulling shank to clamp said tool head non-rotatably to the frontal face of said tool shank.