These steel drills with blunt points (zhuangding or dingzi in Chinese), flat heads (tuozi), or curving heads (wazi) are used for high relief carving, undercutting, and fine shaping of small jade works. The craftsman holds the jade in one hand against the drill, which is mounted on a spinning shaft. He or she rotates the shaft using foot treadles, while continuously applying abrasives, usually sand mixed with water, to the tip of the drill, which cuts the jade.
S. Howard Hansford (Beijing, from 1939) ; Joan M. Hartman-Goldsmith , New York (until 1981)
New York. China Institute in America. "Ritual and Power: Jades of Ancient China," April 19, 1988–June 19, 1988.