Abstract: A machining head for a water jet cutting machine as well as an aiming device equipping such head, includes:an interchangeable tip (28) coupled to a feed source (A) of water under pressure,an acceleration nozzle (22) fixed to the casing (2) and connected to the interchangeable tip (28),a cutting pipe (60) receiving a water jet (J) emitted by the nozzle (22), anda pipe carrier (62) maintaining the pipe (60) relative to the casing (2), such head being characterized in that it includes regulating means (120a, 120b, 112, 94a, 94b) which permit regulation of the position of the pipe carrier (62) relative to the casing (2) in order to adjust the orientation of the pipe (60) in a manner coaxial to the jet (J) emitted by the nozzle (22).