It is proposed that economical performance of diamond bits be quantitatively appraised by use of bit drilling cost.
并提出用钻头钻进成本定量地评价金刚石钻头的经济效果。
Because the drilling cost is not the sole cost of bit, it is necessary to discuss here the highest rotation speed of bit in cutting rock at the lowest drilling cost.
在研究钴进过程的最佳化生产条件中，由于钻探成本的开支不是唯一的一项钻头费用，所以就有必要对最低钻探成本的最高钻头切割岩石的旋转速度进行探讨。
Drilling in gravel stratum is one of present difficulties in drilling area with low drilling speed, short service life of bit and high drilling cost.
卵砾石地层钻进是钻探的难题之一，不仅钻进速度低，钻头的使用寿命短，而且钻探成本高。
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