Fixing bushing assembly for a machining unit and a machining unit adapted to cooperate with said bushing

An assembly comprising in combination:

• a fixing bushing and a machining unit having a nose and a body, the bushing being adapted to receive said nose, said bushing comprising a bore having an inlet mouth and an outlet opening, and, at said inlet mouth, internal guide means and external hooking means and, in said bore, centering means for the machining unit, said unit comprising hooking elements adapted to cooperate with said hooking means of the bushing, and slidable locking means for locking said hooking elements in position for cooperating with said hooking means of the bushing, said inner centering means comprising a substantially cylindrical first portion of the bore of the bushing having a first diameter in the vicinity of the inlet mouth followed by a frustoconical second portion and a frustoconical third portion interconnected by a large bases thereof, and a cylindrical fourth portion defining the outlet opening of the bushing and having a second diameter a little less than said first diameter, the nose of said machining unit comprising in the following order in a direction from an end of the nose toward the body:
• a peripheral chamfer, a first part having a diameter equal to the diameter of said fourth portion of the bore of the bushing, a second part having a diameter equal to the diameter of said first portion of the bore of the bushing, said hooking elements being constituted by a plurality of resilient lugs axially extending form the body toward the end of the nose, each of said lugs having at a free end of the lug means cooperative with said outer hooking means of the bushing, and the slidable locking means comprising a sleeve axially slidably mounted on the body of the unit and surrounding said lugs.