Abstract: The process and apparatus of the invention permits the production of annular parts, such as ferrules, on which machining operations are to be carried out. The process includes the steps of bending a predimensioned metal sheet by a series of internal supports mounted on a rotary plate and by a pressure roller bearing on the outer surface of the sheet. One complete rotation of the rotary plate makes it possible to completely bend the sheet into the form of a ferrule. The second main operation includes carrying out of a welding operation on the two ends of the metal sheet. This process makes it possible to carry out any random prior machining operation on the predimensioned flat metal sheet, without the machining operations being impaired by the bending or welding operation. The process is applicable to the production of front ferrules for casings surrounding the coldest pipe of a double flow turbojet engine.