Adaption of the Tool Design in Micro Deep Hole Drilling of Difficult-To-Cut Materials by High-Speed Chip Formation Analyses

Kirschner, M.1, a; Michel, S.1, b; Berger, S.1, c; Biermann, D.1, d

Institute of Machining Technology, TU Dortmund University, Baroper Str. 303, D-44227 Dortmund, Germany

a); b); c); d)


The chip removal in deep hole drilling with smallest diameters represents a major challenge caused by the limited cross sections of the chip flutes. The production of unfavourable chip forms leads to an accumulation of the chips in the flutes and results in spontaneous tool failures. The application of micro deep hole drilling is even more sophisticated if the machining of difficult-to-cut materials like nickel-based alloys characterised by high strength values and fracture strains is required. In this paper, an enhanced method of analysis to adapt and optimise the tool design with respect to the chip formation in single-lip deep hole drilling with smallest diameters is presented. The fundamental idea of the new analytical technique is the substitution of the surrounding, non-transparent bore hole wall by transparent acrylic glass. This approach facilitates the visualisation of the chip formation at the cutting edges as well as the chip removal along the chip flutes by means of high-speed microscopy. To allow a constant observation of the chip formation and removal process the experiments are conducted with stationary cutting tools and rotating material samples embedded into acrylic glass. The integration of the experimental setup into a conventional deep hole drilling machine as well as the realisation of the visibility despite the constant supply of deep hole drilling oil are shown. Furthermore, the high-speed chip analysis demonstrates the crucial limitations regarding the achievable productivity and process stability using the standardised cutting tool design for single-lip deep hole drilling of nickel-based alloys. Based on these findings, important modifications of the tool cutting edge angles and the centre distance are derived and thus significant process improvements have been reached. The results on the essential chip formation are complemented by analysis of the mechanical tool loads, the tool wear, the surface quality as well as the dimensional and shape tolerances.


Deep hole drilling, Chip, Analysis


7. WGP-Jahreskongress, 5.-6. Oktober 2017, Aachen, Hrsg.: Schmitt, R.; Schuh, G., Apprimus Verlag, ISBN 978-3-86359-555-5, (2017), pp. 29-36