♦Livre♦

Experiments in Egyptian Archaeology: Stoneworking Technology in Ancient Egypt
120. The experiments have demonstrated that problems caused by heat generated by friction do not arise, and quartz sand’s rate of cutting, particularly when used with metal tubes, is slightly better with the sand dry than with it wet. Measurements of the temperature of the test drill-tubes, under load for several minutes, showed a constant drill temperature of approximately 80–100°C. Copper is a good conductor of heat, and this ability to conduct heat upward from the drilling area helps to keep a drill’s temperature low. The experiments with the flat-edged copper saws, in use with sand abrasive, indicate that annealed copper cuts more effectively than hammered copper. (Copper and bronze drill-tubes need to remain fully annealed, whereas a modern, high-speed steel twist drill needs cooling to keep its hardness intact.)