Product Overview
The R32-D32-R32 MF (Male-Female) Rod is a high-performance drilling string component purpose-built for long-hole underground drilling applications, including sub-level stoping, VCR mining, and face drilling in medium-to-hard rock formations.
Unlike conventional extension rod systems that rely on separate coupling sleeves to join rod segments, the MF Rod integrates a male thread (pin) at one end and a female thread (box) at the other into a single continuous body. This eliminates one threaded joint per connection in the drill string, directly reducing energy loss and minimizing the risk of joint failure.
As illustrated in the R32 (1 1/4″) long-hole drilling system, the MF Rod string operates as a direct alternative to the Shank Adapter → Coupling Sleeve → Extension Rod → Coupling Sleeve → Extension Rod configuration — delivering a simpler, more efficient drill string with fewer failure points.
Key Features
Integrated MF — DesignFewer Joints, More Power
By eliminating one coupling sleeve per rod interval, the MF design reduces thread connections in the drill string by up to 50%. This translates directly to higher energy transmission efficiency from the rock drill to the drill bit, and measurably straighter boreholes over extended hole depths.
Optimized Internal Flushing Channel
The precision-bored central flushing hole (diameter D=32mm rod body) maintains consistent water or air flush flow to the drill bit face, ensuring efficient rock cuttings evacuation and bit cooling throughout the hole depth.
ZK22CrNi3Mo Alloy Steel Construction
All R32-D32-R32 MF Rods are manufactured from ZK22CrNi3Mo — a purpose-developed alloy steel for percussive rock drilling tools. Its optimized nickel-chromium-molybdenum composition delivers:
- High core toughness to absorb cyclic impact loads without cracking
- Excellent surface hardness via controlled carburization heat treatment
- Outstanding fatigue strength for extended service life in high-frequency drilling cycles
- Superior wear resistance against abrasive rock formations
Precision R32 Thread Geometry
The R32 threads on both pin and box ends are machined to industry-standard tolerances, ensuring:
- Full thread compatibility with R32 Shank Adapters, Coupling Sleeves, and Drill Bits (Button Bit, Cross Bit, Retrac Bit, X Bit)
- Consistent engagement under intense rotational torque and axial impact
- Resistance to thread loosening and galling under high-vibration operating conditions
Technical Specifications
R32-D32-R32 MF Rod — Full Size Range
| Product Code | Thread | Length (mm) | Length (foot) | Diameter (mm / inch) | Weight (kg) |
|---|---|---|---|---|---|
| 290-3209-5454 | R32 | 915 | 3′ | 32 mm (1 1/4″) | 5.5 |
| 290-3212-5454 | R32 | 1220 | 4′ | 32 mm (1 1/4″) | 7.3 |
| 290-3215-5454 | R32 | 1525 | 5′ | 32 mm (1 1/4″) | 9.0 |
| 290-3218-5454 | R32 | 1830 | 6′ | 32 mm (1 1/4″) | 10.5 |
Thread Standard: R32 (male pin × female box, both ends) Material: ZK22CrNi3Mo alloy steel, carburized & heat treated
Flushing: Center through-hole, water/air compatible Surface Finish: Precision ground rod body
System Compatibility — R32 Long-Hole Drilling Equipment
The R32-D32-R32 MF Rod is a core component of the complete R32 (1 1/4″) long-hole drilling system, which includes:
| Component | Function – Top Hammer Drilling System |
|---|---|
| Shank Adapter | Connects the rock drill (drifter) to the drill string; transfers impact energy and rotation from the hammer to the rods. |
| Coupling Sleeve | Joins two extension rods in a standard threaded system; ensures secure connection and energy transmission between rod sections. |
| Extension Rod | Standard drill string extension piece (requires separate coupling sleeves); used to achieve greater drilling depth in top hammer applications. |
| MF Rod (this product) | Integrated male-female extension rod — eliminates the need for a separate coupling sleeve; faster rod changes, reduced weight, better energy transfer, and lower risk of joint failure in high-frequency top hammer drilling. |
| Guide Tube | Provides borehole directional stability at greater depths; reduces deviation and improves hole straightness in long-hole or deep top hammer drilling. |
| Button Bit / Cross Bit / Retrac Bit / X Bit | Rock-cutting front-end tooling; different designs optimized for specific rock types (abrasive, fractured, hard) to maximize ROP and bit life in top hammer operations. |
System Note: Confirm your Shank Adapter and drill bits are R32-threaded before ordering. MF Rods can be mixed with standard Extension Rod + Coupling Sleeve configurations within the same drill string where required.
Applications
- Underground Long-Hole Mining — Sub-level stoping, VCR (Vertical Crater Retreat), ring drilling
- Tunneling & Drifting — Face drilling and roof bolt installation in medium-to-hard rock
- Raise Boring & Production Drilling — Where drill string simplicity and hole accuracy are critical
- Hard Rock Formations — Granite, basalt, quartzite, and other highly abrasive ground conditions
Maintenance Guidelines for Maximum Service Life
- Thread Lubrication — Apply dedicated drill rod thread grease to both pin and box ends before every connection. Prevents galling, corrosion, and heat-induced seizure.
- Correct Make-Up Torque — Under-torqued connections cause impact energy loss and accelerated thread wear; over-torquing risks thread stripping. Follow rig manufacturer torque specifications.
- Straightness Inspection — Check rods for bend or bow after each shift. Bent rods generate asymmetric stress concentrations leading to premature fatigue fracture.
- Rotation Management — Rotate the leading MF Rod in the string regularly to distribute wear evenly across your rod inventory.
- Storage & Handling — Store rods horizontally on racks, thread-end caps installed. Avoid impacts to thread ends during transport.
How to Select the Right MF Rod Length
| Drilling Condition | Recommended Length |
|---|---|
| Tight underground headings, short lift heights, confined spaces, narrow drifts or restricted access areas | 915mm (3′) |
| Standard sub-level stoping intervals, typical development and production drilling in medium-height stopes | 1220mm (4′) |
| Deep ring drilling, long-hole stoping, high-productivity requirements, large-scale mining operations or vertical/steep dipping ore bodies | 1525mm (5′) or 1830mm (6′) |
For deeper hole applications, calculate the cumulative rod string weight against your drilling rig’s rated feed force and rotation torque to ensure system compatibility.
Related Reading: Rock Drill Rods: Types,Work,Choose & Maintenance
Related Production
Frequently Asked Questions
An Extension Rod requires a separate Coupling Sleeve at each joint, resulting in two threaded connections per join.
An MF Rod integrates the male and female threads into one piece, reducing each join to a single connection — improving energy transfer and reducing assembly time underground.
RockHound's R32-D32-R32 MF Rods use the R32 thread on both ends — the industry-standard thread for 32mm (1 1/4") long-hole drilling systems.
They are fully compatible with all R32-threaded components in the long-hole drilling string, including:
| Component | Compatibility |
|---|---|
| Shank Adapter | ✅ R32 |
| Coupling Sleeve | ✅ R32 |
| Extension Rod | ✅ R32 |
| Button Bit | ✅ R32 |
| Cross Bit | ✅ R32 |
| Retrac Bit | ✅ R32 |
| X Bit | ✅ R32 |
| Guide Tube | ✅ R32 |
If you are unsure of your current thread standard, check your Shank Adapter specification — the shank-to-rod thread type determines the thread standard for your entire drill string.
All MF Rods supplied by RockHound are manufactured from ZK22CrNi3Mo — a high-grade nickel-chromium-molybdenum alloy steel purpose-engineered for percussive rock drilling tools.
Compared to standard carbon steel rods, ZK22CrNi3Mo delivers:
- Higher fatigue strength under high-frequency impact cycles
- Superior core toughness to resist fracture under cyclic axial loading
- Enhanced surface hardness through controlled carburization and heat treatment
- Better wear resistance in abrasive hard rock formations such as granite, basalt, and quartzite
This material specification is the same standard used by leading OEM drill rod manufacturers globally, ensuring RockHound rods perform reliably across the full range of underground drilling applications.
Yes. RockHound R32-D32-R32 MF Rods are fully interchangeable with standard R32 Extension Rods and Coupling Sleeves within the same drill string, provided all components share the R32 thread standard.
Mixed string configurations are widely used in practice — for example, using MF Rods for the deeper intervals of a long hole while retaining existing Extension Rods closer to the collar. This allows you to transition to an MF-based system progressively without replacing your entire rod inventory at once.
An MF (Male-Female) Rod is a single-piece drill string extension that integrates both a male thread (pin) on one end and a female thread (box) on the other — all within one continuous rod body.
In a conventional drill string, connecting two Extension Rods requires an additional Coupling Sleeve at every joint, creating two threaded connections per interval. With RockHound's R32-D32-R32 MF Rod, each connection is reduced to just one — cutting the total number of threaded joints in your drill string by up to 50%.
The result: less energy lost at joints, faster assembly underground, and fewer components to manage in confined working spaces.
RockHound offers the R32-D32-R32 MF Rod in four standard lengths to suit different rig types and underground drilling geometries:
| Length (mm) | Length (ft) | Product Code | Weight (kg) | Best Suited For |
|---|---|---|---|---|
| 915 | 3' | 290-3209-5454 | 5.5 | Tight headings, restricted swing clearance |
| 1220 | 4' | 290-3212-5454 | 7.3 | General-purpose sub-level stoping |
| 1525 | 5' | 290-3215-5454 | 9.0 | Deep ring drilling, high-productivity faces |
| 1830 | 6' | 290-3218-5454 | 10.5 | Maximum penetration rate, large stope geometry |
Selecting the right length: Your rod length should match your rig's feed length capacity and your stope's lift height or burden distance. For deep hole applications, calculate the cumulative weight of your full rod string against your rig's rated feed force and rotation torque before configuring your string.
Contact the RockHound team if you need help sizing your drill string for a specific application.
The three leading causes of premature MF Rod failure in the field are:
1. Insufficient thread lubrication Dry or under-greased connections generate friction heat and metal-to-metal galling at the thread contact surfaces, rapidly degrading thread geometry. Always apply dedicated drill rod thread grease to both pin and box ends before every connection — without exception.
2. Incorrect make-up torque Under-torqued joints allow micro-movement between mating threads during impact, accelerating wear and causing energy loss. Over-torqued joints risk stripping the thread or inducing stress concentrations at the thread root. Always follow the torque specifications recommended for your drilling rig model.
3. Drilling with bent rods A bent rod creates asymmetric bending stress along the rod body with every rotation cycle — the classic mechanism for fatigue fracture. Inspect rods for straightness at the start of every shift by rolling them on a flat surface. Remove any rod showing visible bow from service immediately.
Following RockHound's recommended maintenance protocol will consistently extend rod service life and reduce your total cost per metre drilled.
The R32 female (box) thread at the front end of the MF Rod accepts all standard R32-threaded drill bits. RockHound supplies a full range of compatible front-end tooling for every rock condition:
- Button Bit — Preferred for hard, competent rock; offers maximum penetration rate and long bit life
- Cross Bit — Cost-effective option for medium-hardness or fractured rock formations
- Retrac Bit — Retraction-profile gauge buttons allow easier rod string withdrawal in collapsing or blocky ground conditions
- X Bit — Alternative cross-profile geometry for specific application requirements
For the best system performance, RockHound recommends using matched R32 tooling across your entire drill string — from Shank Adapter through to the drill bit face.