Drilled holes are characterized by their sharp edge on the entrance side and the presence of burrs on the exit side. Also, the inside of the hole usually has helical feed marks. Drilling may affect the mechanical properties of the workpiece by creating low residual stresses around the hole opening and a very thin layer of highly stressed and disturbed material on the newly formed surface. This causes the workpiece to become more susceptible to corrosion and crack propagation at the stressed surface. A finish operation may be done to avoid these detrimental conditions.