One simple way of selecting a drill would be to base it on the hole diameter and depth as shown on the work drawing. The image shows a simplified diagram showing the relationship between the hole depth and drill diameter. For areas that overlap, it is advisable to choose a drill nearer to the centre of the range. However, for economical drilling, workability and productivity are the deciding factors.
In addition, for an efficient drilling performance, factors such as high hole accuracy, long tool life, easy chip breaking and chip control should be considered. Moreover, with the increase in use of NC machines, demand for high speed, high efficiency and high accuracy machining is further increasing. In such a situation, the method for selecting a drill becomes more difficult as factors such as the machine tool and a workpiece material become complex and interconnected.
Therefore, by using the selection lists presented on the previous page ("Selecting a drill") it is possible to select the optimum drill.
Secondly, hole accuracy and a workpiece material are important. Recently, special drills for specific workpiece materials and drills designed for high machining efficiency and accuracy have been developed, allowing even more appropriate use according to the application (See "Drill selection process map").
Finally, it is necessary to choose the correct drill shank type that matches the tool holder and application.
Drill selection procress map