| 摘要 |
PURPOSE: Industrial diamond formed on the tip of a bit for an electric drill is provided to prevent a bit from being broken when drilling a thick steel pipe or thick steel plate with high rigidity. CONSTITUTION: Industrial diamond is formed on the tip of a bit for an electric drill, where the bottom has a male thread portion. The leading end of the rest part of the bit has a female thread portion. Therefore, the male thread portion is precisely mated with the female thread portion to form the whole drill bit.
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