An analytical model for drilling burr formation was developed. The model holds for ductile materials that do not show catastrophic fracture during the plastic deformation of workpiece material for burr formation. The proposed burr formation mechanism was based on the observation of behavior of workpiece materials during drilling of low alloy steel. The model was based on the principle of energy conservation and metal cutting theory. Experimental validation was done, and the results showed good agreement with the model. Based on the model, the effects of several important parameters on burr formation were investigated.