在批林批孔运动深入、普及、持久地发展的大好形势下,我院于74年六月底生产试制了CJ741和CJ742两种φ250毫米的三牙轮钻头。在院党委和工厂车间及研究室党支部的直接领导下,这批钻头在鞍钢大孤山铁矿进行了工业试验。由于得到了矿党委和广大工人师付的大力支持,使现场试验工作进展较顺利。这次试验的结果是:在f=12～14的千山花岗岩中,钻头最高寿命401米,最低 Under the favorable situation of developing the deep, universal and sustained development of the movement of the proletariat and the bore hole, the CJ741 and CJ742 tri-cone roller bits of φ250 mm were trial-produced by the end of June, 74 in our hospital. Under the direct leadership of the party committee of the hospital and factory workshop and the branch of the research laboratory, these drills were tested in the Dagushan Iron Mine in Anshan Iron and Steel. Thanks to the strong support from mine party committees and the vast majority of workers, the on-site pilot work progressed smoothly. The result of this test is: In Qianshan granite with f = 12 ~ 14, the maximum life of the bit is 401 meters, the lowest