A clamp for a tool spindle for rapid interchange of tools without the need to raise the spindle or lower the work further than the end of the tool to allow clearance. The clamp is provided with a recess co-axial with spindle and the tool is provided with an adapter extension movable into the recess in a direction normal to the axis of the spindle or recess. A clamping gate hinged at one side of the recess is then locked to the other side of the recess to complete the recess and lock the tool adapter in position. A locking screw on the gate is then rotated into engagement with a flat on the adapter to integrate the clamping unit and tool. Means are also provided for axial positioning of the tool.