Low pressure drilling
challenges in urban development

The challenges drillers face when drilling in mines and quarries are well documented the world over. Drilling in fractured rock; what to do with an uneven rock floor following a blast; holes that collapse due to an influx of water; heavily fractured rock that eventually collapses; filling a hole, partly or completely, with explosives. Sounds familiar?


With DTH drilling becoming the preferred method in foundation works, well and geothermal drilling, TerraRoc offers a wide range of high-performance equipment for these sensitive and challenging areas.

Terranox DTH hammers

Terranox DTH hammers are designed for optimum performance in low pressure operations. The Terranox hammer is based on well proven technology and over 30 years of successful operations in the industry. When working in urban areas, drilling must often be accomplished during restricted drilling hours. Reducing down time is critical. Terranox hammers are rugged, reliable and, when damaged, easily repaired or replaced. Together with TerraRoc’s worldwide service network, assuring availability of parts, services and support, you can trust this cost-efficient product to do the job for you.


A dedicated package


The Terranox DTH hammers are designed to work with our well proven casing advancement systems: Symmetrix, Elemex and Odex. Together they form a unique in-house turnkey solution for your geotechnical drilling operation, offering reliable and safe geotechnical drilling.

The Terranox product range


The Terranox DTH hammer comes in five sizes. Choosing the right hammer is largely determined by hole size and type of ground conditions. Ideally, the size of the hammer should match the required hole dimension as closely
as possible, leaving just enough space for cuttings to evacuate the hole.

Terranox DTH hammers
DescriptionThread ConnectionOutside diameterRec. hole sizeShank StyleLength without bitWeight without bitPart number
Terranox 3API 2 3/8 Reg PIN793 1/888 - 1053 7/16 - 4 1/8DND90235 1/230668393082635
Terranox 4API 2 3/8 Reg BOX923 5/8105 - 127 4 1/8 - 5DND104941 5/1639868393082640
Terranox 5API 3 1/2 Reg PIN1154 1/2130 - 1525 1/8 - 6DND116645 7/8691528393082650
Terranox 6API 3 1/2 Reg PIN1375 3/8152 - 2166 - 8 1/2DND125549 7/161032278393082660
Terranox 8API 4 1/2 Reg PIN1817 1/8200 / 2707 7/8 - 10 5/8DND144356 13/161773908393082680

Service and tuning kits


In abrasive drilling conditions, partly external components of the DTH hammers are subject for excessive flush blasting and is wearing out before the internal parts reaches their fatigue limits. Wear often appears on the chuck itself or on the cylinder at the chuck-end. For this reason, many of the Terranox hammers are designed with reversible cylinders.


With help of defined service kits, the hammers can be rebuilt, and most internal parts re-used for another run. Use of service kits, extends the total hammer life and substantially reduces the total drilling cost, as the cost for service kits is only approximately 10 % of a new hammer.

Terranox service and tuning kits
DescriptionPart number
HammerService kitTuning kit
Terranox 3839308263583930827238393082728
Terranox 4839308264083930827248393082729
Terranox 5839308265083930827258393082730
Terranox 6839308266083930827268393082731
Terranox 8839308268083930827278393082732
A rule of thumb for use of service kits
Rock formationHammer lifeAction
Highly abrasive< 5,000mUse service kit to rebuild the hammer 1-2 times
Medium abrasive5,000 - 10,000mConsider service kit to rebuild the hammer 1 time
None abrasive> 10,000mRebuilding not recommended, risk that internal parts might fail before the service kit is worn out

Terranox hammers are, for optimized drilling performance and hole cleaning, fitted with choke plugs to enable an ultimate tuning of the hammer for each occasion and use. Replacement choke plugs are included in the Terranox tuning kits.


For easy logistics defined kits containing the vital parts are available for each hammer as to below table.

Matching hammer and casing diameter

For proper selection of Terranox hammer to match casing diameter, please use cross reference table below. Casing size and drilling conditions will be decisive factors when selecting casing advancement system.

Hammer descriptionCasing diameter range
Terranox 3114.34 1/2
Terranox 4139.7 - 152.45 1/2 - 6
Terranox 5168.3 - 177.86 5/8 - 7
Terranox 6193.7 - 244.57 5/8 - 9 5/8
Terranox 8244.5 - 323.99 5/8 - 12 3/4

Selecting compressor capacity


The Terranox hammer range is designed for a maximum working pressure of 25 bar. In overburden drilling applications the air pressure is normally recommended to be kept in the range of 12 14 bars. However, for proper hammer performance throughout the entire drilling operation, the compressor model should be selected to match the corresponding maximum hammer air consumption, shown below.

Hammer descriptionAir consumption (at 24.1 bar)
Terranox 3239506
Terranox 4292618
Terranox 5358760
Terranox 6459973
Terranox 87251538
Above specifications/ratings are based on initial factory setting

Drill rig requirements


For proper hammer performance, the geotechnical drilling rig should be equipped with a rotation unit providing minimum torque as per the table shown below.

Hammer descriptionMinimum torque
Nmlb ft
Terranox 3600440
Terranox 415001020
Terranox 520001480
Terranox 630002210
Terranox 880005900