Hole openers are specialized drill bits that can be used to widen pre-existing size bore holes. At some work condition it may be necessary to increase the size of a pre-drilled hole to a larger diameter or to drill large diameter holes. Hole opener bits are designed specifically for this purpose, which is an effective way of enlarging holes, hence the bits named as "Hole Opener". A common practice involves drilling a relatively small pilot hole at first stage, and second and final stage then further widening it with a hole opener bits, since this can result in a straighter hole and require less powerful machinery. And different stages can be set per drilling specifications to maximize cutting breaking and removal, and rig capabilities. Besides, rotation torque, the DTH hole opener involves a concussive force that repeatedly impact a drilling head into the rock or other substrate. The impacting action can pulverize rock and also force it back and up, helping to clear out the borehole. So, in addition to widening a bore hole, a hole opener can also clean excess material out of it.

The drilling of large boreholes is required in a number of different industries, such as hydrocarbon exploration, well drilling, and horizontal excavation for tunnels and other purposes and so on. Drilling one large hole could require an exceptional amount of power and very large machinery, so the process is sometimes done in several steps. In some cases, a relatively small size bit will be used to drill a pilot hole. This kind of drilling practice typically requires less energy than doing it in one step and can also result in a straighter borehole. After this initial pilot hole has been drilled, a hole opener can be used to widen the borehole. In such case, the result can be a more precise borehole that was created with less powerful equipment than would have been needed to drill a large hole at beginning directly.

Specifications:

	D(mm)	D1(mm)	Gauge	Front	Shank
	165	82	14	14	DHD340     SD4     QL40
	178	99	16	14
	190	115	16	14	DHD350     QL50
	216	138	16	14
	254	159	16	14	DHD360     SD6     QL60
	305	208	16	16
	381	296	16	16
	305	208	16	16	DHD380     QL80
	381	296	16	16
	445	305	18	16	SD10     NUMA100
	482	311	18	16
	660	445	19	18	SD12     NUMA120