Producing quality features with abrasive waterjet milling requires the generation of shallow kerfs with low surface waviness. Typically, such kerfs are produced by deformation wear mode of material removal realized with certain combination of process parameters chosen based on an elaborate experimental analysis. Instead, these parameters can be selected through a modeling methodology developed based on deformation wear erosion theory. As a first part of this development, it is essential to identify the conditions for the prevalence of deformation wear during the generation of shallow kerfs with abrasive waterjets. To establish this condition, this article presents a theoretical analysis of kerf formation formulated based on deformation wear erosion by solid particles. In this analysis, the interaction of the abrasive particles with the material and the subsequent material removal through deformation wear is considered to define the geometry of the cutting front. The geometry of the cutting front was then used to determine the condition at which local impact angle of abrasives striking the cutting front changes to alter the mode of material removal from deformation wear to cutting wear. This analysis has brought out the boundary condition for deformation wear as the maximum depth of kerf to be equal to the average size of the abrasive particles used in the jet. The generic nature of this condition is established with kerfing experiments over three different ductile materials. © IMechE 2017.