There is a high demand for microdrilling processes to drill microholes with diameters equal to or less than 0.2 mm for use in fuel injection nozzles. In this study, nonstep drilling methods are developed for high-efficiency processing. Herein, the effects of the cutting oil supply method and the drill’s feed rate on the developed thrust force and torque during drilling are investigated. Accordingly, it is shown that drop supply of the cutting oil is the optimal method for nonstep drilling because the oil is sucked into the microhole. Furthermore, a high-feed rate is preferred because it produces continuous chips.^*

^* This paper is a translation with revision of the paper: M. Uchiyama and N. Sakata, “Cutting capability of micro drills in non-step drilling 1st report: Optimization of cutting oil supply and drill feed,” J. of the Japan Society for Abrasive Technology, Vol.59, Issue 1, pp. 27-31, doi: 10.11420/jsat.59.27, 2015 (in Japanese).

1. [1] J. Kusaka, “The Future of the Clean Diesel Engine Technology,” JAMAGAZINE, Vol.46, No.3, pp. 9-13, 2012 (in Japanese).
2. [2] The Nikkan Kogyo Shimbun, “Drill Processing Technique to Support High Efficiency Manufacturing,” February 16, 2009.
3. [3] Y. Nanbu et al., “High-Aspect-Ratio Microdrilling Assisted by Uitrasonic Vibration,” J. Jpn. Soc. Precis. Eng., Vol.77, No.3, pp. 306-310, 2011 (in Japanese).
4. [4] H. Ogawa, “Micromachining Using Ultrasonic Cavitation,” J. Jpn. Soc. Abras. Technol., Vol.57, No.7, pp. 432-435, 2013 (in Japanese).
5. [5] N. Sakata and M. Uchiyama, “Cutting Performance of Microdrills Relating to the Cutting Oil,” Proc. of the 1996 JSPE Autumn Meeting, pp. 645-646, 1996 (in Japanese).
6. [6] T. Hosoi, R. Hosoi, S. Hanasaki, and Y. Hasegawa, “A twist drill drillable deep hole under continuously high feed rate,” Jpn. Soc. Mech. Eng., Series C, Vol.58, No.551, pp. 2243-2248, 1992 (in Japanese).
7. [7] Y. Nanbu et al., “High-Aspect-Ratio Microdrilling of Cobalt-Based Superalloy: High-Aspect-Ratio Microdrilling of Nozzle of Marine Diesel Engine,” J. Jpn. Soc. Precis. Eng., Vol.75, No.9, pp. 1083-1087, 2009 (in Japanese).
8. [8] T. Hirogaki et al., “Optimization of Step Micro Drilling Motion with High Speed and Short Stroke in Printed Wiring Boards by Response Surface Method,” Jpn. Soc. Mech. Eng., Series C, Vol.78, No.788, pp. 1280-1294, 2012 (in Japanese).