Xi'an Heaven Abundant Mining Equipment CO.,LTD
If you have spent any time around a rock drilling site, you have probably noticed the long steel bars that connect the drilling rig on the surface to the drill bit working at the bottom of the hole. These bars are drill rods, and they are one of the most important links in the whole drilling system. Choosing the right type of drill rod can mean the difference between smooth, productive drilling and constant downtime caused by broken or worn-out rods.
This guide explains the different types of drill rods, how they work, and how to choose the right one for your project.
A drill rod is a steel extension bar that connects the rock drill, or shank adapter, to the drill bit. It transmits impact energy, rotation, and flushing air or water down the hole. Drill rods are usually hollow so that compressed air or water can pass through the center to clear rock cuttings from the hole.
It is worth noting that the term "drill rod" is also used in the machining industry to describe precision-ground tool steel bar stock used to make punches, dies, and other tooling. These two products share a name but are completely different. This article focuses on the drill rods used in rock drilling, mining, and water well drilling.
A drill rod performs three main jobs in a drilling system:
A good drill rod must therefore be strong enough to absorb repeated impacts, stiff enough to transmit torque without twisting, and precise enough to keep the hole straight.
Drill rods are most commonly classified by how they connect to the bit and to each other. There are three main types: tapered drill rods, threaded (top hammer or extension) drill rods, and DTH (down-the-hole) drill rods.
Tapered drill rods use a simple friction-based tapered connection. One end of the rod has a taper, commonly 7 degrees or 12 degrees, that fits directly into a matching tapered drill bit. The rock drill strikes from outside the hole, and the impact energy travels down the rod to the bit through the tapered joint.
Because the connection is simple, changing bits is quick and easy, which makes tapered rods ideal for jobs that require frequent bit changes. They are commonly used in quarrying, small-section tunneling, and shallow-hole drilling. Tapered rods are typically available in sizes such as H22, H25, and H28, and are often paired with tapered button bits.
At TY Drill Bits, we supply tapered drill rods such as the 7-degree tapered rod (hex22) and the H22 tapered drill rod for rock drilling, along with matching tapered button bits.
Threaded drill rods, also known as extension rods, have threads on one or both ends and are connected end to end with threaded couplings or sleeves. This lets operators build a drill string that can reach tens or even hundreds of meters deep.
As with tapered rods, the rock drill strikes from outside the hole, and the shockwave travels down through each threaded connection. Because every connection is a point of energy transmission, the threads must be machined to high precision and strength.
Threaded rods are the most widely used type of drill rod and are common in mining, quarrying, construction, and anchor bolt drilling. They are classified by thread type, which we cover in the next section.
DTH drill rods work differently from the other two types. In DTH drilling, the hammer is located at the bottom of the hole, directly above the bit. The drill rod's job is to rotate the bit and deliver high-pressure compressed air to drive the hammer and flush out cuttings.
Because they must handle high torque and carry a large volume of air, DTH drill pipes usually have larger diameters and thicker walls than top hammer rods. They are commonly used in deep-hole drilling, water well drilling, and geothermal projects, and are paired with DTH hammers and bits from the DTH drilling tool range.
For threaded (top hammer) drill rods, the thread type is the most important specification, because it determines which shank adapters and drill bits the rod is compatible with. The main thread families are R-thread, T-thread, and HL-thread.
| Thread Type | Rod Diameter | Typical Application |
|---|---|---|
| R22 / R25 | 22 - 25 mm | Light construction, water well |
| R28 / R32 | 28 - 32 mm | Quarrying, medium construction |
| R38 | 38 mm | Quarry production, mid-depth mining |
| T38 | 38 mm | Mining, quarry benching |
| T45 | 45 mm | Deep-hole mining, large-diameter benching |
| T51 | 51 mm | Heavy production mining |
Rod selection should always match the shank adapter and drill bit thread on the same rig. Mismatched thread types cause premature coupling wear and reduce energy transfer efficiency. TY Drill Bits supplies matched rod, shank adapter, and bit sets, including R32/T38/T45/T51 adaptors with hexagon shank and shank adapters for Sandvik and Atlas Copco equipment.
Beyond thread type, drill rods also differ in end configuration and body cross-section:
Drill rods are typically made from high-quality alloy steel. The material must balance two properties: hardness, to resist abrasion from the rock and wear on the threads, and toughness, to absorb repeated impact without brittle fracture.
Manufacturers achieve this balance through careful steel composition and heat treatment. Many quality drill rods are forged hollow and then induction hardened to create a hard outer surface while keeping the core tough and ductile. Threaded ends often receive additional hardening because the connections experience the highest stress concentration.
Understanding why drill rods fail helps you choose and use them correctly. The most common failure modes are:
When selecting drill rods for your project, consider the following points:
Q: What is the difference between a tapered rod and a threaded rod?
A: A tapered rod uses a friction taper connection and is quick to change, making it ideal for shallow drilling and frequent bit changes. A threaded rod uses threaded couplings to build a longer drill string and is better suited to deeper drilling.
Q: What does T38 or R32 mean?
A: These are thread designations. T-thread (T38, T45, T51) is a trapezoidal thread for higher torque and deeper drilling, while R-thread (R25, R32, R38) is a rounded thread for lighter-duty applications.
Q: Can I use any rod with any bit?
A: No. The rod thread must match the shank adapter and the drill bit thread on the same rig. Mismatched threads cause premature wear and reduce drilling efficiency.
Q: How do I know which drill rod I need?
A: The easiest way is to provide the model of your rock drill or impactor, your hole diameter and depth, and the rock type. A supplier can then match the correct rod, thread, and bit.
Choosing the right drill rod is about matching the rod type, thread, diameter, and length to your drilling method and conditions. Whether you need tapered rods for shallow quarry work, threaded extension rods for mining, or DTH drill pipes for deep water wells, working with a supplier that offers a full range of rock drilling tools makes the selection process much easier.
TY Drill Bits (Xi'an Heaven Abundant Mining Equipment Co., Ltd) is a manufacturer and supplier of rock drilling tools based in Xi'an, China. We offer a complete range of drill rods, thread button bits, tapered button bits, DTH hammers and bits, PDC drill bits, and other rock drilling tools, with ISO9001 certification and OEM service. Visit our drill rods page to browse the range, or contact our sales team for help selecting the right rods for your project.
Email to this supplier
About Us
Products
Contact Us
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.
Fill in more information so that we can get in touch with you faster
Privacy statement: Your privacy is very important to Us. Our company promises not to disclose your personal information to any external company with out your explicit permission.
