| 摘要 |
T5936 ROTARY DRILL BIT FOR DRILLING THROUGH STICKY FORMATIONS A drill bit for drilling through sticky formations, such as chalk or marl, comprises a plurality of waterways 4 for transporting drilling fluid and rock flour to the gauge of the bit. These waterways have in downstream direction gradually increasing cross-sectional areas A, the increase of size of said areas along the length of a waterway being at least substantially proportional to the squared radius r thereof from the central axis 10. In this manner the rock flour velocity remains equal or decreases in downstream direction in the waterways so that the risk of rock flour accumulation and compaction is reduced. (Fig. 2) ML5.T5936FF
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