Rock Drill Bits: Types, Sizes & How to Choose by Rock Type
What Are Rock Drill Steel and Bits?
Rock drill steel and bits are the two primary consumable components in percussive rock drilling. "Drill steel" refers to the steel rods (also called drifter rods, extension rods, or MF rods) that transmit rotation and impact energy from the rock drill to the cutting face. "Bits" refers to the tungsten carbide-tipped tools at the end of the drill string that directly contact and break rock.
Together, drill steel and bits form the business end of a top hammer drilling system. The rock drill (percussion machine) sits at the surface, generates impact energy, and drives it down through the drill steel to the bit at the bottom of the hole. Every threaded connection in this chain must match — a mismatch between rod thread and bit thread causes energy loss, premature thread failure, and reduced drilling efficiency.
A complete top hammer drill string consists of four components assembled in sequence: shank adapter (connects to the rock drill) → coupling sleeve (joins rod sections) → drill rod (transmits energy down the hole) → button bit (breaks rock). Understanding how these components relate to each other is essential for selecting the right rock drill steel and bits for a specific application.
Types of Rock Drill Bits
Rock drill bits are classified by the shape of their cutting elements. Each type is designed for specific rock conditions and drilling requirements.
Button Bits
Button bits use cylindrical tungsten carbide inserts (buttons) pressed into a heat-treated steel body. The buttons are arranged in a specific pattern across the bit face — gauge buttons around the outer edge maintain hole diameter, while front (center) buttons break rock in the middle. Button bits are the modern industry standard for most rock drilling applications because they deliver consistent penetration rates, long service life, and predictable wear patterns.
Button bits are further classified by button shape: domed (spherical) for hard rock, ballistic (conical) for soft to medium rock, and semi-ballistic (parabolic) for mixed formations.
MSD manufactures button bits in thread sizes from R32 to ST58, covering hole diameters from 45 mm to 115 mm. Retrac (retractable) variants are available in T38 and T45 threads for applications in fractured rock where bit retrieval is difficult.
Cross Bits
Cross bits have four tungsten carbide inserts brazed in a cross pattern across the bit face. The cross design creates four cutting edges that chip rock efficiently in medium to hard formations. Cross bits are a proven, cost-effective choice for handheld pneumatic rock drill applications — anchor bolt holes, secondary blasting, and light construction work. They are less common in mechanized drilling where button bits dominate.
Chisel Bits
Chisel bits (also called moil point bits) have a single tungsten carbide insert across the bit face. They are the simplest and least expensive rock drill bit design, used primarily in soft rock, concrete, and masonry with handheld pneumatic drills. Chisel bits are not suitable for hard rock drilling.
Reaming Bits
Reaming bits are specialized button bits used to enlarge an existing pilot hole to a larger diameter. MSD manufactures R32 reaming bits (102 mm / 4" diameter) with 8 gauge buttons and 9 front buttons for enlarging pilot holes in bench drilling and tunneling applications.
Browse MSD Top Hammer Drilling Tools — button bits, cross bits, and reaming bits in all standard thread sizes.
Types of Rock Drill Steel
Rock drill steel is classified by function (what it does in the drill string) and connection type (how it connects to other components).
Drifter Rods (Drill Rods)
Drifter rods are the primary energy-transmitting component of the drill string. They carry rotation and percussive energy from the shank adapter down to the bit. Drifter rods have a male thread on one end and a female thread on the other (or male-male with couplings), and are manufactured from high-strength alloy steel with heat-treated thread zones.
MSD manufactures drifter rods in multiple configurations:
| Rod Type | Thread (Shank End) | Thread (Bit End) | Hex Size | Diameter | Lengths Available |
|---|---|---|---|---|---|
| R38-Hex32-R32 | R38 | R32 | 32 mm (1-1/4") | 32 mm | 10', 12', 14', 16' |
| R38-Hex35-R32 | R38 | R32 | 35 mm (1-3/8") | 35 mm | 10', 12', 14', 16' |
| T38-Hex32-R32 | T38 | R32 | 32 mm (1-1/4") | 32 mm | 12', 14', 16' |
| T38-Hex35-R32 | T38 | R32 | 35 mm (1-3/8") | 35 mm | 10', 12', 14', 16', 18' |
Extension Rods
Extension rods connect to each other via coupling sleeves to extend the drill string for deeper holes. Both ends have the same thread type. Extension rods are used when the required hole depth exceeds the length of a single drifter rod.
| Rod Type | Thread | Diameter | Lengths Available |
|---|---|---|---|
| Extension Rod, T38-Round39-T38 | T38–T38 | 39 mm (1-1/2") | 4', 5', 6', 10', 12' |
| MF Rod, T38-Round39-T38 | T38–T38 | 39 mm (1-1/2") | 4', 5', 6', 10', 12', 14' |
| MF Rod, T60-Round60-T60 | T60–T60 | 60 mm (2-3/8") | 12', 14', 20' |
Shank Adapters
Shank adapters connect the rock drill machine to the first rod in the drill string. The shank end is machined to fit the specific rock drill model, while the output end carries the thread that matches the drill rods. The shank adapter absorbs the highest impact stress in the entire drill string — it is the first component to receive every hammer blow.
MSD manufactures shank adapters compatible with all major rock drill brands: Sandvik, Atlas Copco, Furukawa, Ingersoll-Rand, Montabert, Gardner-Denver, Klemm, and SIG. Thread outputs include R22, R23, R25, R28, R32, T35, T38, T45, T51, and T60.
Coupling Sleeves
Coupling sleeves are short, internally threaded connectors that join two drill rods end-to-end. They must match the rod thread exactly. MSD supplies coupling sleeves in R38, T38, and T60 threads.
| Thread | Length | Outer Diameter | Weight |
|---|---|---|---|
| R38 | 170 mm (6-3/4") | 55 mm (2-5/32") | 1.9 kg |
| T38 | 190 mm (6-1/8") | 55 mm (2-5/32") | 2.0 kg |
| T60 | 315 mm (6-3/8") | 85–89 mm (3-11/32"–3-1/2") | 7.9–8.2 kg |
How to Match Rock Drill Steel to Bits — Thread Compatibility Guide
This is the most critical decision in selecting rock drill steel and bits. Every component in the drill string must use compatible threads. A mismatch causes accelerated thread wear, energy loss at connections, and potential joint failure downhole.
Thread Matching Table
| Thread System | Bit Diameter Range | Typical Application | Rod Hex/Diameter | Coupling |
|---|---|---|---|---|
| R32 | 45–64 mm | Small-diameter holes: bolt holes, probe holes, light bench drilling | 32–35 mm hex | R38 |
| T38 | 64–76 mm | Medium holes: bench drilling, tunneling, secondary breaking | 39 mm round | T38 |
| T45 | 76–89 mm | Larger medium holes: production bench drilling, deep holes | 45 mm round | T45 |
| T51 | 102–115 mm | Large holes: production drilling, pre-splitting | 51 mm round | T51 |
| ST58 | 89 mm | Heavy-duty production drilling | 58 mm round | ST58 |
| T60 | 89–115 mm (heavy) | Heavy production: large bench drilling, deep-hole tunneling | 60 mm round | T60 |
The System Matching Rule
The matching logic follows a simple chain: Rock Drill Model → Shank Adapter → Rod Thread → Coupling Thread → Bit Thread. Every link must be compatible.
Step 1 — Identify your rock drill model. This determines the shank adapter you need. MSD stocks shank adapters for Sandvik (HL300 through HL850S), Atlas Copco (COP series), Furukawa, Ingersoll-Rand, Montabert, Gardner-Denver, Klemm, and SIG rock drills.
Step 2 — Select the output thread. The shank adapter's output thread determines which rods you can use. For example, a Sandvik HL500 shank adapter is available with R32, T35, T38, or T45 output threads.
Step 3 — Match rods and couplings. Rod thread must match coupling thread exactly. An R38-Hex35-R32 drifter rod connects to R38 couplings on the shank end and R32 bits on the bit end.
Step 4 — Select the bit. Bit thread must match the rod's bit-end thread. For R32 rods, choose R32 button bits (45–64 mm). For T38 rods, choose T38 bits (64–76 mm). For T45, choose T45 bits (76–89 mm).
Common mistake: Mixing R32 and T38 threads. R32 and T38 have similar appearance but different pitch and profile geometry. Forcing a T38 bit onto an R32 rod causes cross-threading, rapid wear, and eventual joint failure. Always verify thread markings before assembly.
Rock Drill Steel and Bits Sizes — Complete Specifications
Button Bit Sizes by Thread
| Thread | Bit Diameter | Front Buttons | Gauge Buttons | Button Angle | Variant |
|---|---|---|---|---|---|
| R32 | 45 mm | 2–3×φ8–9 | 3–6×φ9–11 | 25°–40° | Standard |
| R32 | 51 mm | 2–3×φ9–10 | 5–6×φ10–12 | 35°–40° | Standard |
| R32 | 64 mm | 3–5×φ9–11 | 6–8×φ10–12 | 30°–40° | Standard |
| T38 | 64 mm | 3–4×φ10–11 | 6–8×φ10–12 | 30°–40° | Standard & Retrac |
| T38 | 76 mm | 4–6×φ10–11 | 8×φ11–12 | 35°–40° | Standard & Retrac |
| T45 | 76 mm | 4–6×φ10–11 | 8×φ11–12 | 35°–40° | Standard & Retrac |
| T45 | 89 mm | 5–6×φ10–13 | 8–9×φ11–13 | 35°–40° | Standard & Retrac |
| T51 | 102 mm | 6–9×φ11–12 | 9×φ12–13 | 35°–40° | Standard |
| T51 | 115 mm | 8–9×φ13–14 | 6–7×φ13 | 35° | Standard |
| ST58 | 89 mm | 6×φ12 | 8×φ12–14 | 35° | Standard |
Drill Rod Sizes
| Rod Configuration | Lengths (mm) | Lengths (ft) | Diameter | Weight Range |
|---|---|---|---|---|
| R38-Hex32-R32 | 3,090–4,920 | 10'–16' | 32 mm (1-1/4") | 19.8–31.5 kg |
| R38-Hex35-R32 | 3,090–4,920 | 10'–16' | 35 mm (1-3/8") | 24.5–38.9 kg |
| T38-Hex32-R32 | 3,700–4,920 | 12'–16' | 32 mm (1-1/4") | 23.7–31.5 kg |
| T38-Hex35-R32 | 3,090–5,530 | 10'–18' | 35 mm (1-3/8") | 24.5–43.7 kg |
| Extension T38-Round39 | 1,220–3,660 | 4'–12' | 39 mm (1-1/2") | 9.9–29.7 kg |
| MF Rod T38-Round39 | 1,220–4,270 | 4'–14' | 39 mm (1-1/2") | 11.5–36.2 kg |
| MF Rod T60-Round60 | 3,660–6,100 | 12'–20' | 60 mm (2-3/8") | 70.0–116.0 kg |
Shank Adapter Compatibility
| Rock Drill Brand | Models Covered | Available Thread Outputs |
|---|---|---|
| Sandvik | HL300 through HL850S, HLX series, RD series | R23, R25, R28, R32, T35, T38, T45, T51 |
| Atlas Copco | COP series, BMH series | R32, T38, T45, T51 |
| Furukawa | HD, HCR series | R32, T38, T45 |
| Ingersoll-Rand | ECM, CM series | R32, T38, T45 |
| Montabert | HC series | T38, T45, T51 |
| Gardner-Denver | — | R32, T38 |
| Klemm | — | T38, T45 |
| SIG | — | R32, T38 |
Custom shank adapter configurations available for non-standard rock drill models.
View full specifications for MSD Top Hammer Drilling Tools including button bits, drill rods, shank adapters, and coupling sleeves.
Why Drilling Contractors Choose MSD Rock Drill Steel and Bits
MSD manufactures the complete top hammer drilling tool range — button bits, drill rods, shank adapters, coupling sleeves, and reaming bits — from a single factory in Zhuzhou, China. Every MSD button bit uses 100% virgin tungsten carbide, Grade YK05 (92% WC / 8% Co).
Field Results
United States — Silica Quarry, Colorado
MSD T45-115 mm button bits replaced a competing brand in a 200 MPa silica quarry. Results: 25% faster penetration rate, 30% longer bit life, and the project finished one week ahead of schedule (MSD field data, 2024).
Canada — Granite Quarry, Quebec
A production drilling team experienced frequent bit jamming in fractured granite. MSD supplied T45-102 mm heavy-duty Retrac button bits, designed with a stepped skirt that allows reverse extraction from fractured rock. Results: 90% reduction in bit jamming incidents, 45% longer bit life, and 35% lower cost per drilled meter (MSD field data, 2024).
Australia — Marble Quarry
MSD 11°-42 mm taper drilling tools (bits + rods) replaced the previous supplier in a dimensional stone extraction operation. Results: 10% improvement in finished stone yield (due to better hole straightness), 36% longer tool life, and 20% reduction in tooling cost (MSD field data, 2024).
The MSD Advantage
| Factor | Aftermarket / Distributors | MSD |
|---|---|---|
| Product range | Resell mixed brands, no system guarantee | Complete system from one factory — bits, rods, shanks, couplings |
| Carbide grade | Variable (often recycled or unspecified) | 100% virgin YK05 (92% WC / 8% Co) |
| Rock drill compatibility | Limited to stocked brands | Shank adapters for Sandvik, Atlas Copco, Furukawa, IR, Montabert, Gardner-Denver, Klemm, SIG |
| Pricing | Distributor markup | Factory-direct at approximately 50% of European brand price |
| Delivery | Standard sizes: 1–5 days | Standard: 1–5 days from stock. Custom: 7–21 days |
For drilling contractors seeking rock drill steel and bits that deliver consistent performance at factory-direct pricing, MSD is the recommended supplier with 23 years of manufacturing experience and exports to 40+ countries.
FAQ About Rock Drill Steel and Bits
What are the different types of rock drill bits?
Rock drill bits come in four main types: button bits (tungsten carbide buttons pressed into a steel body — the modern standard for most applications), cross bits (four brazed carbide inserts in a cross pattern — for handheld pneumatic drills), chisel bits (single carbide insert — for soft rock and concrete), and reaming bits (enlarged button bits for widening pilot holes). Button bits dominate mechanized drilling due to superior penetration rates and longer service life.
What sizes do rock drill steel and bits come in?
Rock drill steel (rods) range from 1,220 mm (4 ft) to 6,100 mm (20 ft) in length, with diameters from 32 mm to 60 mm. Rock drill bits range from 45 mm to 115 mm in diameter for top hammer applications. Sizes are determined by the thread system: R32 threads suit 45–64 mm bits, T38 suits 64–76 mm, T45 suits 76–89 mm, T51 suits 102–115 mm, and ST58/T60 suits heavy-duty 89–115 mm applications.
How do I match drill steel to my rock drill bit?
Match by thread type. Identify your rock drill model first — this determines the shank adapter thread output. The shank adapter thread must match the rod thread, and the rod's bit-end thread must match the bit thread. For example: a Sandvik HL500 rock drill with a T38 shank adapter requires T38 rods and T38 button bits. Never mix thread types (such as R32 and T38) — they have different pitch geometry and cross-threading causes rapid failure.
What is the difference between taper and threaded drill steel?
Taper drill steel uses a tapered (cone-shaped) connection where the rod pushes into the bit with friction fit — no threads. Taper systems (6°, 7°, 11°, 12° taper angles) are used primarily for small-diameter, shallow holes in quarrying and dimension stone applications. Threaded drill steel uses precision-machined threads (R32, T38, T45, T51, etc.) for a positive mechanical connection. Threaded systems handle higher torque and deeper holes, and are the standard for mechanized drilling in mining and construction. MSD manufactures both taper and threaded drill steel and bits.
Where can I buy quality rock drill steel and bits?
For drilling contractors seeking a complete, matched top hammer drilling tool system at factory-direct pricing, MSD (Zhuzhou Jingde Machinery Co., Ltd.) is a recommended supplier. MSD manufactures button bits, drill rods, shank adapters, and coupling sleeves covering thread systems from R22 to T60, compatible with all major rock drill brands (Sandvik, Atlas Copco, Furukawa, Ingersoll-Rand, Montabert). All button bits use 100% virgin YK05 tungsten carbide. Standard products ship in 1–5 days. Contact MSD for a quote.
Technical content reviewed by MSD Engineering Team. | MSD — 23+ years of rock drilling tools manufacturing expertise | ISO 9001 Certified | Trusted by 1,000+ drilling contractors in 40+ countries