RC, DTH, Rotary or Top Hammer? Choosing the Right Drilling Method

Four drilling methods, four different jobs. A plain-language guide to which method fits exploration, blast holes, quarrying and hard rock.

NIKHI GROUP · 11 November 2026

RC, DTH, Rotary or Top Hammer? Choosing the Right Drilling Method

The right drilling method depends on why you are drilling: to sample the orebody, to blast it, or to shape a quarry face. Here is how the four methods we work with compare.

Reverse circulation (RC): for exploration samples

RC uses dual-wall rods. Compressed air travels down between the walls and returns up the inner tube, carrying rock chips to surface where a cyclone collects them. Because the sample travels inside the rod rather than up the open hole, contamination from the hole wall is minimised. RC is a fast, cost-effective choice for exploration and grade-control drilling. Rig for this job: PRD OZ RC (450 m RC capacity, 140 mm holes).

Down-the-hole hammer (DTH): for hard rock

In DTH drilling the percussive hammer sits directly behind the bit at the bottom of the hole, so impact energy is not lost along the drill string. That keeps penetration efficient as holes get deeper, which makes DTH a strong choice for blast holes in hard rock. Rigs for this job: PRD BH 15 100, BH 30 160, BH 45 250 (DTH / rotary), PRD EX 65, PRD HC 500 M.

Rotary: for large-diameter holes in softer formations

Rotary drilling relies on high pull-down force and rotation rather than percussion. It is typically used for larger-diameter blast holes in softer or more fractured rock. Our larger blast hole rigs support both DTH and rotary methods so one machine can cover changing geology.

Top hammer: for small, short holes

With top hammer drilling the hammer sits at the top of the drill string. It is quick and efficient for small-diameter, shorter holes, which is why it is common in quarries and the dimension stone industry. Rig for this job: PRD HC 500 D (38–45 mm holes, up to 3 m).