ing F is nature of the substrata. Heretofcre core drilling could threaded, while to this the core barrel is attached. be done only with diamond bits. Now, thanks to the Either the shot bit or the cutter can be threaded into the lower end of the core barrel. The shot bit, which efforts of an… … out of an old 3 structure at 4Feer the New York LONG Aqueduct. The high-priced tool. Mr. Davis’ first attempts were di- shct bit made rected to the construction of a toothed bit or cutter its way easily made ot hardened steel. With this he was very suc- through the cessful in soft and moderately…
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