Innovative Design

Dual Tube Reverse Circulation Drill Rods


Connector Tubes NOT required
Matrix dual tube drill rods do not require connector tubes. The inner tube simply makes up and breaks out with our welded tool joints. Inner tubes are recessed inside the tool joints protecting them from handling damage. Drillers report easier, faster, and safer pipe handling particularly on angled holes.

Premium Material Selection
We understand that the best drill rods must always begin with the best raw materials. Reliability and long life are built into Matrix dual tube drill rods by using the best made in the USA materials available. Matrix chooses high-strength, oxidation resistant chrome-moly (CrMo) 4130 alloy made to our own dimensional and chemical specification. Mid-bodies use cold drawn over mandrel (DOM) mechanical tubing which has been stress relieved to ensure dimensional stability and minimize the probability of crack initiation. Tool joints are heat treated for optimal strength and wear resistance. Inner tube ends are also heat treated and O-ring sealing surfaces are burnished for better seal life. Aluminum, titanium, and steel hybrid alloy materials are also chosen for specialized projects.

Advanced Thread Design
Threads are the most critical element in the drill string. They must resist all the stresses of drilling, endure the wear and tear of make-up and break-out, and in the case of dual tube, must do this with a minimum wall thickness to maximize annular air flow and sample return. All Matrix threaded connections incorporate unique design features to achieve superior performance.


Torque capacity of a joint largely depends on its shoulder area. Matrix maximizes this area by implementing a proprietary “double-shoulder” design   consisting of an internal shoulder in addition to the usual external shoulder. This design optimizes coupling strength and gives each rod a greater fatigue resistance extending the service life of each drill rod, while reducing total cost of ownership.

Matrix implements 2 start and 3 start threads in our designs for enhanced makeup/breakout speed. These thread designs use a “Dual-Radius Thread Form” allowing the thread-root radius to be lengthened for increased strength. We have also optimized the taper of each thread for improved torsional strength and more stabbing control.

Another important aspect of our thread design is our stress-relief groove machined above each pin thread. This groove safely redirects the tensile and torsional stresses that would normally be concentrated at the last engaged thread over a larger surface area, thus minimizing the probability of surface crack initiation.

In addition to all these design optimizations, Matrix also implements a controlled steel shot peen operation on all threads. This process generates beneficial compressive residual stresses thus increasing resistance to corrosion, fatigue, fretting, galling, and improves lubricant retention.

Plasma Arc Welding

Matrix has over 35 years of experience with dual tube welding. As an essential element of drill rod design, welding must be planned and executed for reliability. Here at Matrix we have designed our products utilizing the best and most reliable welding process available. To ensure 100% penetration, welds on both outer and inner tubes are made with a state-of-the-art computer controlled plasma arc cold wire-feed welding process (PAWCWF). This high-energy density process is similar to laser or electron beam welding, in that it produces a “keyhole” during welding. This technically superior “keyhole” process generates visible 100% penetration, while also providing high strength welds with minimal heat input. The Matrix welding process gives significantly better results compared to the competition.

Check out the process in action! This video was shot at our facility in Rexburg Idaho.

Inner Tube Stabilization System
MATRIX’s unique design supports the inner tube on a wide, rugged shoulder inside the outer tube, which assures the inner tube is locked into its proper position and cannot rotate or come out. The inner tube is supported without the need for cutting and welding slots in the outer tube, eliminating potential air leaks and stress risers. MATRIX also features a stabilizing system for the inner tube placing a high-strength, vibration damping material between the inner and outer tubes, effectively isolating the inner tube from excess stresses and minimizing the vibrations within the string.


  • “Matrix has helped us tremendously over the years. The team at Matrix doesn’t roll its eyes or make excuses when it comes to figuring out a custom drilling solution. They really latch on to this stuff and get excited about solving our problems! To have a supplier like that is huge.”

    Chris DelahuntyVP of Operations, DOSECC Exploration Services