Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Sapphire as a Single-Crystal Cutting Tool for Machining Ferrous-Based Optics

Amit Dodmani1, Sathyan Subbaih1 and A. Senthil Kumar2,a

1Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600036, India

2Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, 117575, Singapore


Ultra-precision machining produces smooth optical surfaces with nanometric surface finish using a single crystal diamond (SCD) tool. SCD tool can maintain very sharp and uniform cutting due to its high hardness and is used to machine nonferrous alloys, plastics, and polymers. However, excessive tool wear occurs when a SCD tool is used for cutting ferrous alloys because of carbon's chemical affinity towards iron. Many techniques like cryogenic turning, ultrasonic vibration cutting, and ion implantation techniques are used to suppress the SCD tool wear. But, in this study we use an alternate single crystal tool to machine the ferrous optics. Single crystal alumina (Sapphire) is selected as a cutting tool material because of its hardness and availability in bulk size. A lapping setup is developed to fabricate a sharp cutting-edge sapphire tool with zero rake and 7° clearance angle. The cutting-edge radius on sapphire tool obtained is comparable to the SCD tool edge radius. Orthogonal cutting of steel is performed in an ultra-precision machining facility using these sapphire tools and SCD tool. The surface finish on the workpiece, and cutting forces are studied for different depths of cut and cutting speeds. Comparison of sapphire and diamond tool performance during orthogonal cutting of steel in terms of surface roughness and cutting forces is studied.

Keywords: Sapphire, Orthogonal cutting, Single-crystal diamond tool

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