Montabert drifter HC110

Drilling Methods- Drifters

Drilling methods with drifters & rock drills : How to choose the right drill for your application?


Drifters, hydraulic rock drills, hard rock hammers & top hammers are destined to be fitted on specific drilling machines & mining equipment like Atlas Copco, Secoroc, Sandvik, Tamrock, Minemaster, Resemin, MTI, Fletcher, Montabert, Wolf, AMV, Robodrill, CAT, Caterpillar, McDowell, Herrenknecht, Furukawa, GHH, FRD, DH Mining, Boart Longyear, Joy, RDH, Terex, and many others. All manufacturers names, numbers, prices, symbols and descriptions are used for reference purpose only.

Top hammer rock-drill or DTH Hammer?

If you are considering integrating a brand new drill in your equipment range, there are a number of factors before making the decision. Rock typology, budget, mining or quarrying site configuration, anticipated future applications, noise, desired hole dimensions, existing machines and available time are all factors that you simply should take under consideration before considering that purchase. We are about to define a number of the main variations between hydraulic top hammer rock drills (drifters), and down the hole (DTH drills) or in the hole (ITH drills).
The mechanical distinction between the to typologies of drills is where the hammer is located within the equipment. The percussive devices (hammers) apply cyclical shock waves to the drill bits. In case of down the hole drills, the percussive device is placed in direct contact with the bit, and is therefore inside the borehole: “down-the-hole”. Top hammer rock drills, however, apply these repeated shock waves at the top of the drill string, outside of the bore.
The main overall distinction between the two equipments is that top hammer rock drills are more efficient at depths up to 40 meters deep and get the job done faster. It is important to also consider the fact that the operating cost of DTH drills is often higher. Both kind of drills can be operated in soft and medium as well as hard ground while top hammers drifters perform better in very hard rock, particularly in fractured hard rock. Rock drill, however, has an excellent performance in soft ground, in this case the accurate choice would be to consider a rotary drill.
DTH drills are usually powered with pressurised air, the overall system efficiency is very low, becoming gradually lower when the drilling depth increases. Top hammer rock drills use hydraulic energy with a very high system efficiency which remain unchanged in any drilling conditions. On the other hand, DTH drills are more mechanically efficient as less energy is lost in the transmission of shock waves from the hammer to the drill bit (within couplings of the drill string).
While in top hammer rock drills, part of the energy is lost going down the way along the drill steel. The repeated shock waves from the hydraulic hammer on couplings and rods of drill string’s top drifter gradually wear the couplings and rods, proofing that top hammer drills usually require more consumables in the long run.
With advance drifters technologies, a hydraulic dampener contributes to reduce the wear of the drill steel: The stress on the drill string is drastically reduced allowing a longer life span of the shank adapter, the couplings, the rods and the drill bit.
Hydraulic top hammer drills are better adapted to narrow and short bores (up to 40 meters), they drill quicker and much more efficiently than DTH drills. One important drawback of DTHs is that their minimum hole diameter is about 3 inches, while top hammer drifters are able to drill holes with diameter as low as 1 inch.
As the drifter stays outside the hole while drilling, top hammer drills have no risk to remain stuck inside the hole during drilling operations, their life span is also much longer than DTH drills. Hydraulic top hammer rock drills are usually less accurate than DTH drills but they can incorporate anti-jamming devices like Roxar reverse percussion which reduce jamming risk.


If you are an equipment manufacturer looking for high drilling speed and low operation cost, in fractured rock as well as in hard rock, top hammer drifters, like Roxar drifters should be your ultimate choice. Our experts are skilled and experienced in supporting equipment manufacturers with selecting the perfect drill for their equipment or specific applications. We understand that each application is completely different and every customer has unique factors to consider when selecting a rock-drill. Get in touch with Roxar and we will analyse your requirements and budget to find the best solution.

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