Professional Rock Drilling Rods

An integral drill rod — also called an integral drill steel — is manufactured as a single, one-piece component. The chisel bit head, rod body, and hexagonal shank are all forged and machined from the same bar of alloy steel with no threaded connections. A coupled rod system, by contrast, uses separate shanks, extension rods, and bit holders joined by threaded couplings.

The integral design offers higher energy transmission efficiency (typically >95%), eliminates the risk of joint loosening or uncoupling in wet conditions, and produces less rotational energy loss. The trade-off is that integral rods are limited in total drilling depth — once all rods in a step-down set are exhausted, depth cannot be extended further without switching to a coupled system.

The step-down sequence is the standard drilling method for integral rods. Because the rod and bit are one piece, the bit diameter must be slightly larger than the rod body to allow the rod to advance into the hole. As you drill deeper and switch to a longer rod, that longer rod must fit inside the hole already drilled — so its bit diameter must be fractionally smaller than the previous rod's bit diameter.

In practice, the bit diameter decreases by approximately 1mm with each step. For example, using Series 12: start with the 800mm rod at Ø40mm, follow with the 1,600mm rod at Ø39mm, then the 2,400mm rod at Ø38mm, and so on. Skipping steps or using rods out of sequence risks jamming the rod in the formation, which can result in a lost rod and a damaged hole.

The right series depends primarily on your target hole depth and the required starting hole diameter. As a general guide: Series 12 is the most versatile for deep holes requiring a large starting diameter (Ø41mm starter, up to 6,400mm total depth). Series 11 offers the greatest reach in this range (up to 7,200mm) with a narrower diameter profile (Ø34mm starter). Series 13 and 16 are short, stiff sets best suited to secondary breakage, shallow blast rounds, and anchor drilling where depth is not the primary concern. Series 17 is the preferred choice for high-production dimension stone cutting where a large starting gauge (Ø40mm) and short rod length are both required. If you are unsure which series matches your rock conditions and drilling depth, contact our technical team with your drill pattern specifications and we will recommend the appropriate set.

The H22×108mm shank is compatible with the following common handheld and stopper pneumatic rock drills: Y24, YT24, YT27, YT28, and equivalent models from major OEM manufacturers that specify a Hex 22mm (7/8") chuck with a 108mm drive length. Before placing an order, verify both the hex size and the drive length in your drill's technical documentation. Some older or non-standard drill models may use a different drive length (e.g., 82mm) even with the same 22mm hex — these are not interchangeable.

ZK55SiMnMo is a high-alloy drill steel grade developed specifically for percussive rock drilling applications. The designation reflects its core composition: approximately 0.55% carbon (providing base hardness), with silicon (Si), manganese (Mn), and molybdenum (Mo) as primary alloying elements. Silicon enhances elastic strength and resistance to softening under heat. Manganese improves hardenability and toughness. Molybdenum increases fatigue strength and resistance to temper brittleness under cyclic loading.

The combination is critical for integral drill rods because the shank end must be hard enough to resist wear inside the chuck, while the rod body must remain tough enough to absorb thousands of high-energy blows per minute without developing fatigue cracks. Inferior steel grades with insufficient alloy content fracture prematurely at the shank shoulder — the highest-stress point in the rod geometry.

The most reliable field indicator is penetration rate. When your penetration rate drops by 20–30% compared to a freshly ground bit under the same rock conditions and drill settings, the bit requires regrinding. Visually, a worn chisel insert will show a flat, rounded cutting edge rather than a sharp, well-defined chisel profile. Do not wait until the rod stalls — drilling with a dull bit dramatically increases lateral stress on the rod body, overheats the carbide, and accelerates fatigue cracking. Most integral rod chisel inserts can be reground 5–8 times before the insert height is insufficient for further dressing.

Water flushing is the standard and strongly recommended method for all integral rod drilling. Adequate water flow through the drill's flushing hole keeps the carbide bit cool, evacuates drill cuttings from the hole, and reduces airborne dust. Dry drilling significantly shortens bit life and rod service life, and generates respirable silica dust that poses a serious occupational health hazard. Ensure your rock drill's water valve and internal flushing channel are clean and unobstructed before each shift. Minimum recommended flushing water pressure is typically 3–5 bar, depending on hole depth.

Service life varies considerably depending on rock type, drill operating parameters, and maintenance practices, and is best measured in meters drilled rather than hours. In medium-hard granite with proper lubrication and regular bit regrinding, a well-maintained integral rod set can be expected to deliver several hundred meters of total penetration across the full step-down sequence. The factors with the greatest negative impact on service life are: drilling with a dull chisel bit (increases lateral stress on the rod body), insufficient drill lubrication (accelerates shank wear), misaligned collaring (introduces bending fatigue at the shank shoulder), and storage corrosion (initiates subsurface cracking). Addressing these four factors consistently will have a greater effect on cost-per-meter performance than any change in product specification.

Our standard range covers the five series listed in the specification table, which encompasses the most common drilling sequences used in quarrying and mining worldwide. Custom configurations — including non-standard lengths, modified bit geometries, or alternative shank dimensions — are available on a minimum order quantity basis. Please contact our technical sales team with your required specifications, target rock type, and annual volume estimate for a feasibility assessment and quotation.