当钻头上下钻时，要把钻孔保持在中心。
Keep the drill centred in the borehole while it ascends and descends.
钻头通常属于刮刀型，装备有PDC或者天然金刚石切削齿，但取芯钻头的特别之处在于钻头中心有一孔。
The bit is usually a drag bit fitted with either PDC or natural diamond cutting structures, but the core bit is unusual in that it has a hole in its center.
这样允许钻头围绕岩石的中心圆柱体钻进，并通过钻头进入取芯桶。
This allows the bit to drill around a central cylinder of rock, which is taken in through the bit and into the core barrel.
应用推荐