TEMPERATURE-MEASUREMENTS UPON THE CHISEL SURFACE DURING ROCK CUTTING

In the laboratory, temperature measurements have been made upon the chisel surface and inside the chisel during rock cutting on moderately strong sandstone (UCS 19.5 MPa) and limestone (UCS 25.2 MPa), to study chisel wear during rock dredging. For the measurement of the temperature upon the chisel surface, a special thermocouple configuration has been developed. With the sandstone block the temperature on the chisel surface increases up to approx. 550-degrees-C at the end of the block and with the limestone block up to approx. 800-degrees-C. At a distance of 0.5-1.0 mm from the chisel surface, these maximum temperatures decrease to values of approx. 120 and 250-degrees-C, respectively. The length of the saturated block is 2.5 m and the cutting velocity is 2.5 m/sec. The extent of chisel wear on the sandstone block is small and limited to parallel tracks and polished edges. On the limestone block, however, large plastic deformations are visible.