在中硬以上岩层中,用普通合金钻头扩孔,存在如下缺点:①容易崩刃;②合金片磨损快,难于保持孔径.因而扩孔效率很低,又大量消耗钻头.原因是:合金片镶在钻头底部同一平面上,由于钻具的振动,合金片受力不均,且受冲击;合金片数量少,每颗合金片受力较大.针对这一情况,我队锡山分队在实际生产中设计了一种锥度为1∶20的锥形合金扩孔 In the above hard rock, the use of common alloy bit reaming, there are the following disadvantages: ① easy to chipping; ② alloy wear fast, difficult to maintain the aperture, which reaming efficiency is very low, but also consume a large number of bits. Inlaid at the bottom of the bit on the same plane, due to the vibration of the drill, alloy sheet uneven force, and by the impact; small number of alloy pieces, each piece of alloy stress greater .In response to this situation, our team Xishan detachment in actual In production, a taper alloy taper of 1:20 was designed