Abstract: An automatic tool changer mechanism for a machine tool in which the tool is supported in an adapter having a tapered spindle-engaging end and an opposite tool-engaging end, and provided with a generally annular-shaped flange, intermediate its ends, having a generally V-shaped groove in the circumferential face thereof, a plurality of adapters being disposed in a magazine from which they may be selectively withdrawn and transported by means of a suitable transport mechanism to the spindle of the tool machine for use thereat, in which the adapter is supported, both in the magazine and during transport by means of cooperable jaws associated respectively with the transfer mechanism and the magazine, with such jaws being adapted to engage and support the adapter at such flange.