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过去使用钻铤都是用一根0．5米的短钻杆与粗径钻具连接,往住在短钻杆处发生折断事故,并易造成孔斜。
In the past, the drill collars were all connected with the large-diameter drill by a short drill rod with a length of 0.5m. A breakage accident occurred in the short drill pipe and the hole was easily inclined.