Abstract
The mechanics of the formation of exit burrs for drilling metals are analyzed. A burr formation model is developed where the material in front of the drill is modeled as a circular plate of varying thickness. The drilling thrust force is distributed as a pressure along the plate. Material removal continues until a failure condition is reached. At the point of failure of the plate the remaining material is bent out to form the burr. The model also includes temperature effects. Experimental verification was conducted on 2024-T351 aluminum and on 7075-T561 aluminum. Two types of drill geometry were considered. The model accurately predicts the trends in the data However, the burr formation model over predicts the magnitude of the burr due to the failure criteria chosen and the limitations of elastic plate models.
