A waterjet system for generating and delivering fluid jets suitable for processing a workpiece has a cutting head body and a mixing tube. The cutting head body includes a mixing chamber and a bore. The bore is positioned downstream of the mixing chamber, and an abrasive fluid jet from the mixing chamber passes through the mixing tube. The mixing tube has a first coupler adapted to magnetically couple the mixing tube to the cutting head body when the mixing tube is installed. The cutting head body has a second coupler positioned to engage the first coupler of the mixing tube to keep the mixing tube properly positioned during operation of the waterjet system.