The invention relates to a process for piecing on a machine for producing core spun yarns, said process comprising the following successive steps of: taking off a broken end of a core spun yarn formed from the receiving member, (for example a reel); exposing the internal core of said yarn over a pre-determined length; connecting the core thus exposed with the end of the elementary core yarn; introducing the bared core into the fiber distribution system; distributing the fibers on the core downstream of the point of join; and advancing and winding normally. The invention also relates to a device for carrying out this process.