Abstract: Feed screw for feeding a mix, said screw consisting of a core part (1), which becomes thicker towards its trailing end, and of a screw spiral (2) that revolves around said core part. The feed screw is provided with a detachable tip portion (3) at its thicker end. The detachable tip portion (3) is a sleeve-shaped piece, which is supported on an inner part (4) that constitutes a projection on the frame part of the feed screw. The frame part includes at least one front face (6) which, when the machine runs and when the screw revolves, pushes ahead of itself a counter-face (7) provided in the tip portion (3) and transmits the torque to the tip portion.