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This paper describes the top structute of Mode C down-the-hole butten bit, including the top shape, fragments blowdown space, butten shape and but-ton distribution, etc. 文中對(duì)C型潛孔柱齒鑽頭頭部的耑麪形狀、排渣空間、柱齒形狀及分佈等問(wèn)題加以闡述。