The influence of flute form on drill design and performance

Many modifications have been made in the past to the conventional drill points and references to the better performance of curved lip drills when cutting cast iron can be found. Similar drill points do not seem to be as successful with steel. The objective of this research was set to analyse drill design and to study the effect on drill performance of changing the drill conventional flute form when cutting steel. Changing the conventional flute form has an immediate effect on the shape of the drill lip - it is no longer a straight cutting edge. A new range of problems arises when the drill lip is a curved line as the available expressions in literature for drill cutting angles calculation are not valid except for straight lines. However, to be able to calculate and to predict the cutting angles with a nonconventional flute drill is a matter of necessity, especially if the new flute design is based or specified upon some condition relative to these angles. The drill lip shape is also influenced by the flank surface. Thus the analysis of the drill lip shape and the calculation of the cutting angles cannot be made without studying both the flute and the flank surfaces. Geometric surfaces are better deal with by computing techniques and computers. Thus the shape of a drill lip - the intersection of the flute with the point flank - and the cutting angles, are analysed by means of computer design aids for both varying flute and point flank surfaces. [Continues]