An Altenative method of Coating Carbide Tods (Lengthening the Life of Coated Carbide Tods Subiect to Vibration during High Speed Cutting)

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The authors found out in the first two yeard after the Grant-in-Aid for Scientific Research had started helping this research project that the life of cemented carbide tools coated with ceramics is significantly lengthened by exposing the carbide substrate as a narrow band along the cutting edge on the rake face. In this year, practical industrial methods to expose the narrow band in industry were discussed. Two exposing methods were attempted. One was to grind off the ceramic coating at the edge by inclined surface grinding. The other was to remove the ceramics by honing so that a round substrate edge with a controlled radius was formed. Tools made by both methods were tested by intermittent high speed cuttings.The following results were obtained.(1) For the first method it was found by varying the inclined angle from 0゜ to 45゜ that tool life reached a sharp peak when the exposed part is inclined by 16゜.(2) The second method to expose the substrate at the cutting edge was found to be very effective to extend the tool life. When the height of exposed rake and width of exposed band were made within 12 to 22 <micrn>m and within 70 to 90<micrn> m,respectively, the tool life was lengthened 6 times to 9 times longer than that of conventional tools.(3) To discover why these methods were able to improve performance, the propagation of cracks was traced by SEM and temperature distrbution was measured. Although there was no difference between Rex tool and conventional tool in temperature distribution, there was a great differece between them in the process of tool failure.