In this article we examine the effects of structural dynamics on the surface figure of flycut parts. A model is presented that incorporates the machine tool structural loop dynamics and the loading that results from intermittent contact of a rotating diamond cutting tool with the workpiece. The model output is shown to accurately predict the workpiece flatness obtained in a series of cutting trials carried out with a high-speed flycutting spindle. The model is then used to predict workpiece flatness under a variety of cutting conditions. The results indicate that workpiece flatness is highly dependent on the relationship between the spindle speed, the dominant resonant frequency within the structure, and the swept angle of the interrupted cut. The results provide insight into how a flycutting operation may be designed for best results.