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.

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。

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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.

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。

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