Match the Rock Drill to the Hole You Have to Drill

Size the drill to the hole: a 9 lb class drill handles holes to 1-1/8 in. diameter and 18 in. deep; a 15 lb class reaches 1-1/2 in. x 24 in.; a 30 lb class 1-3/4 in. x 36 in.; a 45 lb class 2 in. x 72 in.; a 60 lb class 3 in. x 96 in.; and the 80 lb class S83 reaches 4 in. holes and 25 ft of depth. Beyond 4 in. or 25 ft, the conversation moves to rigs or down-the-hole hammers – call us. Class labels are an index of blow energy, not exact tool weight: actual weights in the line run from 8 lb (CP 0009) to 72 lb (S83).

Between 19 and 146 CFM at 90 psi, by class: 9 lb drills draw 19-28 CFM and run off a small portable compressor; 15-30 lb drills draw 32-73 CFM; 45-60 lb sinkers draw 85-130 CFM; and the underground drills draw up to 146 CFM, with the S83 jackleg spec’d for a compressor of at least 185 CFM. A 185 CFM tow-behind runs any single handheld drill in the line with margin. The pressure that matters is at the tool inlet, not the compressor gauge – use at least 3/4 in. ID hose up to 100 ft and 1 in. beyond, or a 100 psi compressor can deliver 70 psi at the drill.

They are the same percussion drill supported three different ways. A sinker drills downward, fed by the operator’s weight through the handles. A jackleg mounts the drill on a hinged pneumatic feed leg that carries its weight and pushes it forward, for horizontal and inclined holes underground. A stoper points straight up on a rigid leg for overhead work like roof bolting. Parts and drill steel largely interchange across all three.

Wet, wherever silica exposure is in play: water injected through the drill steel suppresses respirable dust at the bit, cools the bit, and improves cuttings removal. OSHA’s construction silica rule (29 CFR 1926.1153) and MSHA’s mine rule both set a 50 microgram permissible exposure limit, and wet drilling is the engineering control of choice. That is why wet configurations exist across the line – S83 wet, APT 137/155 factory wet versions, the water kit for the CP 0032A, and the water-flushed BBC 16W. Dry drills remain appropriate where exposure is otherwise controlled or the substrate carries low silica risk.

The chuck decides. The 9 lb drills take 3/4 in. round-shank steel with integral whirlibits. Everything bigger takes hex shanked rods in three cross-brand standards – 7/8 x 3-1/4, 7/8 x 4-1/4, and 1 x 4-1/4 in. – tipped with threaded carbide cross bits or button bits. Because the standards are shared, your existing steel and bits carry over between an APT, Toku, Texas Pneumatic, CP, or S83 drill with the matching chuck. Carbide button bits improve penetration 25-50 percent over integral steels in Atlas Copco’s published comparisons.

A rock drill bores holes: it adds automatic rotation and through-steel flushing to percussion, which is exactly what chipping hammers and paving breakers lack. A chipping hammer (7.9-22 lb in our line) is a surface tool for cleaning, scaling, and controlled concrete removal. A paving breaker hits far harder with no rotation, for breaking slabs and rock mass. If the job is a round, sized, clean hole – anchor, blast, or utility – it is a rock drill job. Some 9 lb drills (the CP 0009 A and F trims, APT 109, TX-C9) include a rotation shut-off so one tool can do both light drilling and chipping.