Reverse Circulation Performance Tooling

Reverse-Circulation (RC) drilling is used to collect rock samples quickly and efficiently using a large rotary drill and air compressor. The high speed and lower cost per meter of RC drilling makes it ideal for obtaining mineral samples in the early phases of an exploration project.

Reverse Circulation Drilling Rods

Boart Longyear offers drill rods in both Metzke and Remet-type threads for complete compatibility with other systems. Our robust drill pipe provides 360° of contact from inner tube collar to outer tube, and is designed to be easily replaced in the field, minimizing costly downtime.


Metzke-type thread is one of the recognized standard threads used in reverse circulation drilling. Boart Longyear Metzke-type drill pipe features high-grade alloy tool joints and inner tube assemblies, and easily replaceable inner tubes with special joints that offer superior stabilization with minimal flow restriction. Metzke-type thread uses a strong 4 threads per inch design and more robust 90° tool joint mating surface.


Remet-type thread is another recognized standard in RC drilling. Boart Longyear Remet-type drill pipe features high-grade alloy tool joints and inner tube assemblies. Its easily replaceable inner tubes with special joints offer superior stabilization with minimal flow restriction. Remet-type RC pipe features sealing o-rings on the pin portion of the inner tube assembly, providing optimal inner tube sealing and airflow.


Boart Longyear RC subs feature precision cut threads that ensure long life and compatibility, and our use of hardened alloys and precision machining maximize drilling economy and increase productivity. For customer convenience, we keep common subs in stock all year long.

There are an infinite number of combinations when looking at RC subs—diameter, thread type, configuration, length—the list below is only a representation of popular types we keep in stock. We also make custom subs and provide sub blanks for our customers to machine to their own specifications.

Saver Subs

A saver sub is usually positioned at the top of the rod string, between the first rod and the top drive head assembly, and protects the top drive head threads from the high number of make/breaks during drilling. It is more economical and productive to wear a saver sub versus the threads on the top drive head. Typically, the box thread is the same as the pin thread and standard lengths are 150mm and 300mm (shoulder to shoulder).

Adapter Subs

Adapter subs are used to adapt one size diameter and / or one type of thread to another. custom adapter subs are available - tell us what you need and we will find a solution.

Digout Subs

Positioned between the down hole hammer and the rod string in a pure RC system, adigout sub provides hole stabilization through the pads positioned on the outer diameter while connecting the rod string to the down hole hammer in the event that thread types between the two are different. The outer diameter of the stabilizing pads (or blades) is based on the size of hole being drilled and is typically sized 1/8” smaller than the outer diameter of the bit.

Cross-over Subs

Also referred to as an interchange sub, a cross over sub is positioned between the down hole hammer and the rod string in a conventional RC system. Its primary purpose is to allow an entry point for the sample as it travels from the bit face to the inner tube. In the event that the thread connection between the rod string and the hammer are different, the interchange sub also serves as an adapter sub.

Blow-down Subs

When required, a blow down sub is placed at the top of the rod string once it has been disconnected from the top drive head. It’s used to direct the airflow down the inner tube to clear a sample blockage.

Blow-up Subs

Also known as a blow back sub, a blow up sub is used to direct the airflow up the inner tube (through the head to the sample collection tube) to clear a blockage. When required, it is placed at the top of the rod string once the rod string has been disconnected from the top drive head.

Tri-Cone Subs

A tri-cone sub, also referred to as a roller bit sub, is positioned at the bottom of the rod string in a tri-cone system, connecting the string and the bit. It is available in two configurations: as an adapter sub to connect the rod string to the tri-cone bit in overburden drilling applications (referred to as a tri-cone bit sub) or as a sub with fitted inner tube to allow the sample to be directed up the inner tube to the surface for collection in an exploration system (referred to as a roller bit sub).

Drive Subs

The drive sub is positioned between the head saver sub and the rod string to hold the head wear tube in place. It can also be used as an adapter sub between the top drive head and the saver sub.


Used in either pure RC drilling or conventional DTH methods, our swivels are a cost effective alternative to conventional top & bottom swivel operation, and with only one set of connections, they provide additional safety benefits and lower maintenance requirements.

image_galleryAuto Blow-down

The Auto Blow-down unit has the purpose of clearing a sample blockage in the inner tube below the drill head. In the event that the sample clumps together, causing a blockage while traveling up the inner tube, the Auto Blow-down directs air flow down through the inner tube with the goal to clear the blockage. This action is completed conveniently by the operator from the control panel.

image_galleryDeflector Box

All reverse circulation systems require a deflector box type unit that has 2 functions: provide a transition between the inner tube assembly and the sample tube while slowing down the sample traveling at a high rate of speed up the inner tube assembly. The Boart Longyear deflector box unit employs high technology and robust construction to provide maximum life and efficiency. The Boart Longyear unit is constructed of high grade hardened alloy steel with replaceable ceramic pads that provide additional wear resistance and longer life.

image_galleryKnock-on System

The knock-on system is required to be added to the deflector box unit, providing a connection point between the deflector box and the sample tube. The sample tube, secured to the knock-on system through the use of a hose tail and collar system directs the gravel-like sample to the sampling equipment.


Boart Longyear offers a warranty for its Reverse Circulation Tooling.

The BLH5-55RC hammer is at the cutting edge of rock drilling technology and offers high performance, outstanding reliability, simplicity, and low operating costs. The advanced design of the BLH5-55RC hammer balances the piston and bit weight, resulting in more energy being transferred into the rock and less into the drill string and rig. The low cost, foot valve-free, and robust BLH5 bit delivers unmatched reliability and life to keep you drilling in the hole longer.

Heavy Duty and Lightweight Bit Design

  • Larger shank spline cross section reduces risk of shank-off through splines.
  • Small and lightweight bit design makes handling the bit safer.

High Performance and Reliable Hammer Design

  • Valved drive stroke delivers maximum impact, power, and efficiency versus fixed piston port designs.
  • Uniquely heat treated steel valve technology eliminates the risk of melting that is associated with plastic valves, making it more reliable and longer lasting.

Reliable and Durable Collection Tube

  • Extra hard material is durable and extends the life of the collection tube.
  • Isolation mounts prevents hammer vibration from interfering with the collection tube.

High-Frequency Cycle

  • Lower striking energy works well through clays and other similar ground conditions and is less prone to plugging.
  • Weight matched piston and bit recovers impact recoil energy into piston improving efficiency and reducing vibration to the drill string and head, potentially reducing rig maintenance costs.

Tri-Flow Cuttings Removal

  • Advanced design evenly balances air flow across the bit face for better samples.

Other features

  • Damped check valve movement reduces lip seal wear and check valve spring fatigue.
  • Unique design eliminates need for secondary adaptor to secure collection tube.

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