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本刊通讯员报道:上海工具厂为北京水箱厂试制直径为4.9mm,长度为132mm的直柄超长左旋磨槽钻,经使用效果良好;并为长春
Our correspondent reported: Shanghai Tool Factory for the trial of Beijing Tank Factory diameter of 4.9mm, length 132mm straight shank long left-handed grinding groove, the use of good results; and Changchun