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以往有人认为“在坚硬致密的岩层中，应该使用小粒的钻粒钻进”，但是，几年来我队在10—11级的坚硬致密矽化变质砂岩、闪长岩，石英脉中实际钻进的结果证明，使用大粒度的钻粒（4.0—4.5毫米）钻进比使用小粒度的钻粒（2.5—3.0毫米）钻进效率要高21％，其理由如下：（一）一定材料的钻粒其抗压强度是随钻粒粒度的大小而决定的，钻粒粒度愈大，其抗压强度也大，钻粒粒度愈小，其抗压强度也小，其关系根据材料力学上的理论计算，钻粒的抗压强度公式为：
In the past, people thought that “drilling of small grains should be used in hard and dense rock formations.” However, in recent years, our team has actually drilled in hard and dense silicified metamorphic sandstones, diorites and quartz veins of grades 10-11 The results demonstrate that drilling with large grain sizes (4.0-4.5 mm) is 21% more efficient than drilling with small grain sizes (2.5-3.0 mm) for the following reasons: (i) Drilling of certain materials Its compressive strength is determined by the size of the grain size of the diamond. The larger the grain size of the diamond is, the larger the compressive strength is. The smaller the grain size of the diamond is, the smaller the compressive strength is. The relationship is calculated according to the theory of material mechanics , The formula of compressive strength of drill grain is: