<P> Drilled holes are characterized by their sharp edge on the entrance side and the presence of burrs on the exit side (unless they have been removed). Also, the inside of the hole usually has helical feed marks . </P> <P> 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 . </P> <P> For fluted drill bits, any chips are removed via the flutes . Chips may form long spirals (undesirable) or small flakes, depending on the material, and process parameters . The type of chips formed can be an indicator of the machinability of the material, with long chips suggesting poor material machinability . </P> <P> When possible drilled holes should be located perpendicular to the workpiece surface . This minimizes the drill bit's tendency to "walk", that is, to be deflected from the intended center - line of the bore, causing the hole to be misplaced . The higher the length - to - diameter ratio of the drill bit, the greater the tendency to walk . The tendency to walk is also preempted in various other ways, which include: </P>

What functions are performed by the flutes on a drill