BIT WEAR AND CUTTING FORCE IN ROCK CUTTING
The paper describes a fundamental investigation on bit wear and cutting mechanism in rock cutting comparing with those in mortar and metal cuttings. Turning-operation (facing) test previously developed by the authors were modified and used in this study. Main modification was made to measure cutting forces in three orthogonal directions by a newly attached dynamo-meter.
A series of laboratory tests were carried out. Forty-seven rock samples, two mortars and five metals (mild steel, cast iron, copper, brass, aluminum) were tested in the study. Five kinds of cutting bits/chips made from three kinds of WC, a cermet and a ceramic were used. A measurement of cutting force and bit wear were successfully performed and main results can be summarized as follows;
1. Cuttings of rock is relatively small and granular.
2. Bit wear is evident in rock cuttings and small in metal cutting.
3. Cermet and ceramic bits are easily failed by chipping in rock cutting, indicating that potentially the proposed testing method can be applied to evaluate durability of bit material.
4. Cutting component of resultant tool force is comparatively large in rock cutting.
5. Ratio of forces, (cutting-component)/(thrust component), is almost the same for all samples.
6. The ratio does not change even if bit wear is proceeded.
KEY WORDS: Rock, Cutting, Turning-operation, Cutting Force, Bit, Wear