Twisted deep hole drilling tools for hard machining

•A holistic consideration of twisted deep hole drilling tools for hard cutting operations.•Tool's symmetry is of vital importance for the bore hole quality and the performance.•Asymmetries are caused by manufacturing flaws with corresponding tolerances in the range of a few microns.•Only highly symmetric tools result in high process reliability without tool failure.•Slightly asymmetric tool tends to wear out unequally during the tool life time and premature failure results.

The availability of high performance twisted deep hole drilling tools has been a significant innovation achieved some years ago. The use of these tools in machining centres permits substantially higher productivity and flexibility compared to existing deep hole drilling tools or alternative manufacturing processes for holes with a high aspect ratio. The aim of the present work is the systematic consideration of twisted deep hole drilling tools for reliable and economical hard cutting operations with a high level of quality assurance. In particular, a detailed analysis of manufacturing flaws and tolerances in tool making as well as their influences on the tooĺs performance and the dynamic process behaviour has been conducted. It is shown that twisted deep hole drilling tools can be successfully applied not only with a high productivity but also for a high quality production of hardened components. A prerequisite to this, however, are holistic and precisely controlled process steps including appropriate clamping devices and a suitable high pressure lubrication strategy as well as the availability of high performance tools manufactured with high precision and low tolerances. In this context the symmetry of the tool shown to be of vital importance for the tooĺs performance and the quality of the drilled holes.