In this paper, the mechanisms of material removal during the fluidized bed machining (FBM) of polymeric substrates are analyzed. Cylindrical components composed of polyvinyl chloride (PVC) were exposed to the impact of abrasives while rotating at high speed within a fluidization column. The interaction between the Al2O3 abrasive media and the PVC surfaces was studied to identify the effect of the main process parameters, such as the machining time, the abrasive mesh size, and the rotational speed. The change in the surface morphology as a function of the process parameters was evaluated using field emission gun—scanning electron microscopy (FEG-SEM) and contact gauge profilometry. An improvement in the finishing of the processed surfaces was achieved, and the related mechanisms were identified. The roles of the impact speed and the contact conditions between the abrading particles and the substrate were also investigated.