| 摘要 |
A drill beam comprises a pipe on which assembled of separate parts shell is placed, this is made of material with hardness higher than hardness of material of the pipe. Total length of the free, not deformed shell is larger than the length of the pipe measured between the ends of the upper and the lower adapters. One of component parts of the assembled shell has cuts altering with each other in height in chess order. Such implementation of drill beam makes it possible to decrease consumption of material.
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