Materials that are difficult to cut require the use of a water jetting nozzle with an abrasive entrainment chamber. A high pressure water nozzle inside the assembly creates a water jet. This pressurised water jet travels through the entrainment chamber at high speed to a focussing nozzle dragging the air in the chamber with it and creating a vacuum. Abrasive material is fed into the side of the chamber under air pressure. The abrasive particles are sucked into the air around the water jet and accelerated into the water stream to emit from the focussing nozzle.