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Research Papers

Analysis of the High Performance Drilling Process: Influence of Shape and Profile of the Cutting Edge of Twist Drills

[+] Author and Article Information
W. Koehler

 Robert Bosch GmbH, Karl-Fey-Str. 13, 70499 Stuttgart, Germany

J. Manuf. Sci. Eng 130(5), 051001 (Aug 14, 2008) (7 pages) doi:10.1115/1.2951932 History: Received March 17, 2005; Revised May 08, 2008; Published August 14, 2008

The aims of the investigations presented in this paper were to measure the tool load under conditions of high performance drilling and to analyze if changes of the tool edge shape as well as the edge profile significantly influence the edge stresses. The described methods to analyze the influences of edge shape modifications will contribute to the optimization of drilling tools. Based on a specific cutting edge shape of a drilling tool, systematic changes to the tool’s chamfer and the transition from the chisel edge to the cutting edge were made. Forces and temperatures on the cutting edge were measured as well as the heat flow into the chips and the workpiece. Using a quick-stop device, chip roots of the different drill tools under conditions of high performance machining were made in order to analyze the chip formation. The contact between chip and rake face could be made visible by a so called contact area analysis. It could be shown that the modification of the transition from the chisel to the cutting edge influences the orientation of the forces on the drill. Machining with a rounded cutting edge shape compared to a chamfered edge reduces the mechanical and thermal tool load. This is confirmed by the fact that the deformation zone in front of the cutting edge is smaller as shown by the crosssections of the chip roots. The presented experimental methods show the possibility of determining influences of modified cutting edge shapes and to adapt the drill to the needs of the high performance drilling.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Variations of the basic twist drill a (cutting edge shape and profile), definition of cutting angles

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Figure 2

Experimental setup for the analysis of the mechanical load distribution on a drilling tool

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Figure 3

Calorimetric measurement setup to determine the chip heat in drilling according to Schmidt (19)

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Figure 4

Experimental setup to record the thermal energy emitted in the feed direction of the drill during drilling the test piece (realized and schematic setup)

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Figure 5

Systematic used to generate defined cross sections of chip roots

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Figure 6

Torque and feed force of test tools—influence of different cutting edge shapes and profiles

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Figure 7

Influence of the cutting edge profile on the distribution of the cutting force components along the cutting edge

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Figure 8

Heat removed by chips compared to total heat, influence of different cutting edge shapes and profiles

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Figure 9

Heat development in the workpiece, influence of the cutting edge shapes and profiles at f=0.25mm

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Figure 10

Cross sections of chip roots of the transition between the chisel and the major cutting edge

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Figure 11

Influence of the cutting edge shape on the formation of the contact area and the chip formation—formation of low loaded areas at the back of the edge on the rake face

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Figure 12

Influence of the cutting edge shape on the formation of the contact area and the chip formation at a feed of f=0.375mm

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Figure 13

Material and heat flow in front of the cutting edge with formed stagnation zone

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