For successful abrasive waterjet cutting, there are several factors at the cutting head that determine the precision and quality of the waterjet stream and will affect the quality of part you are able to cut with an abrasive waterjet. There are other factors that will go into cutting a precise and accurate part (machine design, controls, software and high-pressure pump) that will be discussed in other chapters. This chapter will focus on the cutting head and the waterjet as it interacts with the work piece.