Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts (1880)
D. Appleton and Company, Benjamin, Park, 1849-1922 · New York, D. Appleton · leaf 714
ant stream of water is forced down through the hollow drill-rod, thereby keeping the bit cool andthe hole bored clear of sediment, which is forced by the water-pressure up the outside of the rodsto the surface. The hollow bit is a steel thimble, having three rows of diamonds (bort or… … diamonds of the first-mentioned row cut the path of the drill in its forward progress, while thoseupon the outer and inner periphery of the tool enlarge the cavity around the same, and admit thefree ingress and egress of the water, as above described. The screw-shaft, being rotated and fed forward,…
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