Burr Produced on the Drilling Process as a Function of Tool Wear and Lubricant-Coolant Conditions

This work shows the resulting height and shape of the burrs produced by drilling holes with ratio L/D = 3. The tool used in the tests was the solid twist HSS drill coated with TiAlN, with diameter of 10 mm, to drill the microalloyed steel DIN 38MnS6. The height of the burr was studied under different lubricant/coolant systems, namely: dry machining, use of Minimum Quantity Lubrication (MQL) at the flow rate of 30 ml/h, and fluid applied in the conventional way (flooding). The following cutting fluids were used: vegetable oil (MQL), mineral oil (MQL and flooding) and semi-synthetic oil (flooding). The trials were carried out at two cutting speeds (45 and 60 m/min) and the criterion adopted for the end of the test was the catastrophic failure of the drill. The results showed that the height of the burr increases primarily with the wear of the tool and that this increase is almost exponential after 64% and 84% of drills life, for the speeds of 45 and 60 m/min, respectively. Furthermore, the results generally showed that the smallest burr height was obtained for the dry machining and the largest for the MQL systems.