Single Jack Miner
According to Frank Crampton, in his book "Deep Enough" 1982 University of Oklahoma Press, "After mucking came instruction in single and double-jack drilling. Usually hard rock stiffs could work double or single as they chose....Double jacking was impossible in narrow stopes less than sixteen to eighteen inches wide, where the holes to be drilled were mostly overhead anyway...They taught me how to point drill holes, and why; and to drill without going-by and breaking my hand, if the single jack missed the steel drillhead. Pointing each drill hole was damned important. Swinging the ordinary four-pound single jack fifty times a minute, for hours at a time was bad enough, but John T trained me on what he called a "Dago" which weighed four and one-half pounds and had a tapered face smaller than the regular single jack hammer head. The fewer holes one had to drill, the less work there was to do: drilling with the "Dago" and pointing holes so that each would break out the most rock was the answer."
Experienced single jack miners struck the drill approximately 50 times per minute, while rotating the drill a 1/4 turn between hammer strikes.
Photo provided by LunaCommon.org - UCR California Museum of Photography