INTRODUCTION
Earth Drills
Earth drills are powered by hydraulic motors, which operate using the machine’s auxiliary hydraulic system.
Hydraulic oil flows into the motor via the supply line and exits through the return line. This oil flow and pressure generates the power needed to turn the motor, which is directly coupled to a planetary gearbox. Unlike the motor, the gearbox has its own oil reservoir, which must be changed at regular intervals to maintain performance and longevity. Hover over (or press, for mobile devices) on the headings below to highlight each part of a Digga earth drill.
CASE DRAIN
Why use one?
A case drain is needed in some hydraulic motors to manage internal leakage, heat buildup, and pressure balance.
Internal leakage & pressure relief
All hydraulic motors have some internal oil leakage due to clearance between components. This leakage is necessary for lubrication but can cause pressure buildup inside the motor casing. A case drain line allows excess oil to escape, preventing seal damage and motor failure caused by excessive pressure.
Heat dissipation
Hydraulic motors generate heat during operation, and excessive heat can damage seals and reduce efficiency. The case drain allows a small amount of oil to circulate out, carrying heat away and helping with cooling.
Balancing shaft seal pressure
Motors without a case drain rely on internal pressure balancing, but high backpressure in the return line can force oil past the shaft seals, leading to leaks. A case drain maintains a low-pressure zone inside the motor casing, protecting shaft seals from excessive pressure differentials.
High-pressure applications
Motors operating at high pressures or high duty cycles often require case drains because they experience greater internal leakage and heat buildup. This is common in radial piston, bent-axis, and high-performance Geroler/Gerotor motors.
Without a case drain
Blown case and/or shaft seals due to pressure buildup, overheating (reducing efficiency and lifespan), and premature motor failure from excessive internal pressure.
MOTOR & GEARBOX
Ratings
Each hydraulic motor is assigned a power rating, which is expressed in either kilowatts (kW) or horsepower (hp). This rating reflects the motor’s ability to handle a specific combination of hydraulic flow rate (measured in litres per minute, or LPM) and hydraulic pressure (measured in BAR). To ensure optimal performance and longevity, it’s important to understand the two main limits that define the motor’s power capabilities:
- Max Flow @ Max Allowable Pressure
This figure indicates the highest level of combined flow and pressure that the motor can tolerate safely. For example: A motor rated at 115 LPM at 130 BAR equates to approximately 25 kW of input power. - Max Pressure @ Max Allowable Flow
This value shows the highest hydraulic pressure the motor is designed to handle, based on a specified flow rate. Example: 240 BAR at 60 LPM also results in around 25 kW of hydraulic power.
⚠ Exceeding the motor’s maximum kW (hp) rating can result in motor or gearbox failure.
Flow vs Pressure
- Flow (LPM)
This determines how fast the hydraulic motor spins — in other words, it controls the rotational speed of the motor. - Pressure (BAR)
This determines how much torque, or turning force, the motor and gearbox can deliver under load.
Compact design
The compact design of Digga’s smaller earth drills compared to others, allows for greater working length underneath (and around) for augers, enabling earth drills to go down the hole for added drilling depth.
Because we design and manufacture each part inhouse, rather than assemble off the shelf components like others, our earth drills are superior quality.
Why we make our own
Digga earth drills use Digga-manufactured gearboxes with exceptionally tight tolerances. Precision components are temperature-controlled during assembly to ensure perfect fit, delivering superior strength, smoother operation, and longer service life than imported alternatives.
Quality, service & reliability guaranteed
Our world-renowned earth drills are manufactured in our company-owned and operated state-of-the-art factories.
Using only the highest grade material and with the strictest of quality control methods, Digga gears, components, and attachment range are produced inhouse through 15 CNC and VMC machining centres, 15 gear cutting machines, and extensive state-of-the-art steel fabrication & robotic processes.
TURN YOUR EARTH DRILL
Into a Torque Head
Add the Digga Energy Control Valve (ECV) to your earth drill to enable safe and efficient screw piling. The ECV protects your drive from damage caused by sudden hydraulic kick-back when a pile hits target torque. It redirects built-up pressure, allowing the anchor to safely unwind and reducing wear on your motor and gearbox.
WHAT IS
kW? And why it matters
Every hydraulic motor fixed to a planetary gearbox has a listed maximum power (kW) rating. Exceeding this rating will cause motor damage and failure.
kW Power can be calculated with the following formula:
(kW) = Flow (litres/minute) × Pressure (bar) ÷ 600
2-Piece shaft design
With more than double the side load capacity of competitors, Digga’s two-piece shaft design ensures bearings carry load efficiently without added stress.
The separate shaft isolates planetary gears from pushing, pulling, and bending forces, giving the highest pullout rating in the industry, secured with a heavy-duty custom lock nut.
Efficient radial piston motor
Digga’s PDHP and SD-XD range use radial piston motors which are volumetrically superior to any other motor on the market today, and more contamination resistant than axial piston motors. Capable of withstanding Case drain pressures three times our nearest competitor. Ratio – 2:1 two-speed.
EARTH DRILL
Couplings
Flush Face Couplings – Designed for minimal leakage and better contamination control, making them ideal for cleaner hydraulic connections. However, they can be more difficult to connect or disconnect under pressure.
Poppet Couplings – Allow for easier pressure relief, making them simpler to connect and disconnect, but they are more prone to leakage and contamination compared to Flush Face couplings. Choosing the right type depends on the application and operating conditions.
Replacing threaded fittings
First, Identify the type of coupling (flat face, or poppet style), then measure the external diameter of the machine’s male coupling. Finally, measure the internal diameter of the threaded side (female BSP).
Measuring couplings
First, identify type of coupling (flat face, or poppet style). Then, measure the diameter of the male coupling on the machine. Fractional body coupling sizes are industry standards, and are not to be used as actual coupling measurements. Example: A 3/8″ male poppet coupling measures 17mm – Not 9.5mm as the fraction would indicate.
2-Speed (PDT)
Digga’s 2 speed drilling auger drives for High flow machines have been designed for a wider range of applications. Offering a high speed, low torque setting for the smaller auger jobs when you need that extra RPM, and low speed, high torque for when you really need to grind out that larger diameter hole. It’s like having 2 drive units in 1.
VIS motors are 50% more efficient than gear motors, resist contamination, handle 70kW (95Hp), higher pressures than 6K Series, and 2-Speed models boost high-speed/low-torque by 50%.
Advantages of rotary bored pier holes
Over screw anchors
Rotary bored pier holes can generally support greater loads per pier than screw anchors, and can be drilled to greater depths than screw anchors. They are more robust, which means they can be used in more challenging soil conditions, and can provide greater stability.
The choice between foundation screw anchors and rotary bored pier holes will depend on specific site conditions and the requirements of the project. Ultimately, a professional engineer should be consulted to determine the best foundation system for your project. But, whatever method you choose, Digga will have you covered.
EARTH DRILL
Frequently Asked Questions (FAQs)
What earth drill best suits my machine?
General rule of thumb would be that your machine weight matches the model code of the earth drill.
i.e. 2 Tonne Machine – PDX2, 3 Tonne – PD3, 5 Tonne – PD5, etc., etc...
Your application and expectation would be the next governing factor.
i.e. For a 5 Tonne machine
The standard model reference of PD5 would best suit augering in general conditions of soil, clay, shale up to approx. 900mm.
Should your main drilling requirement only be for softer ground conditions with smaller diameter augers, e.g. sand and soil with augers up to 600mm dia., then you may consider stepping down a model size to a PD4-5, (-5 denotes 75mm Square Output Shaft to match the recommended Type 6 Auger Bits). This step down in model will give you more auger speed while still maintaining enough power to cope with the down-pressure of the 5 Tonne machine.
Likewise, if your application requires larger dia. holes or harder condition, i.e. rock, then stepping up a model or two, PD6 or PD7 may best suit these applications.
What is the biggest earth drill I can put on my machine?
There is a several factors that are at play when suiting up “The Biggest earth drill” consideration needs to be given to:
- Lift capacity of the host machine: should the weight of the drill exceed the SWL (safe Working Load) of the host machine then the drive should not be fitted.
- Ground clearance: Careful consideration needs to be given to insure there is ample ground clearance under the pickup of the host machine when both the drive and drilling tool or Screw Pile are fitted.
- Application Overview: When selecting the largest drive, it's essential to consider both the desired outcome and the specific job requirements. These factors will significantly influence the choice of the appropriate drill.
What is kW and why does it Matter?
Every hydraulic motor fixed to a planetary gearbox has a listed maximum power (kW) rating. Exceeding this rating will cause motor damage and failure.
Power is created by combining pressure and flow. You may increase pressure while reducing flow, or increase flow while reducing pressure – maximise both simultaneously may exceed the motor's safe operating limits. The kW Power can be calculated with the following formula (kW) = Flow (litres/minute) × Pressure (bar) ÷ 600
Operating outside the rated kW will cause:
- Excessive heat buildup, degrading hydraulic fluid
- Internal seal and shaft damage
- Motor seizure and failure
- Costly downtime and replacement
What happens if put the wrong drive on my machine?
If you install the wrong planetary earth drill on your machine, several issues could arise, potentially affecting performance, safety, and the longevity of both the drive and the machine:
- Incorrect Torque and Speed: The earth drill may not be suited to the hydraulic flow and pressure of your machine. This can result in too much or too little torque, either leading to inefficient digging or overstressing the drive components leading to frailer.
- Reduced Efficiency: The wrong drill might not be optimized for your specific drilling conditions, causing slower digging and increased wear on the auger teeth and pilot, leading to more frequent maintenance.
- Hydraulic System Strain: Using an incompatible drive could place excessive strain on your machine's hydraulic system, potentially causing overheating or damage to pumps, hoses, and other components.
- Poor Performance: If theearth drill is mismatched, it may not provide the required torque or rotational speed for your ground conditions, leading to subpar hole performance, especially in difficult ground.
- Increased Wear and Tear: An incorrect drive can accelerate wear on both the drill and the auger, leading to more frequent breakdowns or even failure, which can be costly and time-consuming to repair.
- Safety Hazards: A mismatched drive may cause unexpected behaviour, such as uncontrolled movements or failure under load, which could create a safety risk to operators, bystanders and equipment.
For optimal performance and safety, it's crucial to match the earth drill to your machine's specifications and the ground conditions you are working in.
What are the advantages of a 2-speed earth drill?
A 2-speed drill offers enhanced versatility and efficiency for drilling applications by providing two selectable speed ranges:
- High Torque (Low Speed): This setting is ideal for drilling through hard, compacted ground, clay, or rock. It delivers maximum torque, allowing the auger to cut through tougher materials with greater force, though at a slower speed.
- High Speed (Low Torque): This setting is suited for softer soils, such as sand or loam, where high torque isn't necessary. It allows for faster drilling, increasing productivity by completing holes more quickly in easier ground conditions.
Benefits of a 2-Speed Drive:
- Versatility: Allows you to switch between speed and torque depending on the ground conditions, making it suitable for a wide variety of drilling environments.
- Efficiency: Saves time and wear on equipment by using the appropriate speed and torque for each specific task.
- Enhanced Versatility and Performance: Engineered to handle both hard and soft soils, this design allows for the integration of a larger reduction gearbox, delivering increased torque without compromising speed. Enjoy the performance benefits of two earth drills in one, eliminating the need for equipment changes and significantly boosting overall job efficiency.
In short, a 2-speed drill offers greater diversity, control, and adaptability, ensuring optimal performance and productivity across different drilling conditions.
Can one earth drill fit both my machines?
It is possible to get an earth drill that can be used with two different size machines, but it will depend on the specific earth drill and the machines you have. If your two machines are close in size, for example a 5t and 10t or 15t and 20t but the drill must be suited to the larger machine, it is not feasible should you have a 3t and 20t machine as the physical size of the drive for the 20t machine is far too large for the 3t machine and the performance output would be inadequate to perform normal drilling.
Some earth drills are designed to be used with a range of different machines and may come with adaptors or other attachments that allow them to be used with different sizes of equipment. However, it's important to check the specifications of the earth drill and the machines you must ensure that they are compatible.
Additionally, it's important to consider the power and torque of the machines, and the size and weight of the earth drill. A larger or heavier earth drill may require a more powerful machine to operate, and a smaller machine may not be able to handle the weight and torque of the earth drill.
It's important to consult with the manufacturer or a professional before deciding, and to check the compatibility and capacity of your machines with the earth drill you want to use.
The other option that is idea for this scenario of running one drive two machines is a two-speed drive (see 2- Speed high flow & 2-Speed STD flow).
Will my 1.0Tonne machine dill a 600mm Dia. hole in solid rock?
In general, we would have to say NO - For the following reasons:
- Without knowing the grade of rock, e.g. for sandstone there are 5 grades, 1 – being soft and weathered, classed as drillable, and 5 – being extremely hard and classed as un-drillable.
- The physical downforce of your machine will not carry enough weight to functionally drill this diametre. hole in rock.
What is the difference between a PD5, PD6 & PD7?
There are several differences between a PD5 & PD6, PD7
The main is the amount of torque outputted by each individual unit PD5 Max. Nominal Torque @ 240bar Pressure is 5000 Nm., PD6 – 5,500 Nm & PD7 – 6,000 nm.
With each increment in increase of torque you have an equal decrease in output shaft speed when inputting the same amount of flow (Lpm or Gpm).
Additional differences between the PD5 and the PD6 & PD7 is the gearset of a PD5 has a Series 2 Gearset where the PD6 & PD7 have a series 4. This difference is in the thickness of the gearsets in each. These differences are there to cope with the increasing weight of the parent machine and for the increase in torque capabilities.
Also, there is a marked difference in the bearings size of the PD6 & 7 over the PD5. The increase in size of the bearings in the PD6 & 7 is to cope with the increase in weight from the parent/host machine.
What is better, Round, Square or Hex Shaft?
Depending on the torque output of the drive unit we would recommend a square or hexagonal shaft for all drives over 4,500 Nm. For drives under this torque rating a 65mm Rnd as standard relies on the auger pin to bare the rotational load of the drive unit. This pin is rated to 10Knm but with our safety factor we like to step up to Sq or hex for torques higher. By using sq. or hex we are supporting the rotational load of the drive on the four side of the square or the 6 sides of the hex.
Why does my earth drill need servicing?
The gearbox of earth drills sit in their own bath of oil. The gearbox is not lubricated by the machines hydraulic oil, as a result the oil needs regular changes similar to your car.
Service intervals are outlined in the operator’s manual provided with all Digga attachments. The recommended intervals depend on the intensity of use, ranging from occasional to extreme. For best practices, consult the manual to determine the appropriate maintenance schedule based on your specific usage.
Regular servicing is essential to maintain performance and extend the life of your equipment as well as your warranty.
What oil do I use in the gearbox?
Depending upon the earth drill model being used and its application with determine the type of oil to be used, but in all drive, we recommend using and “EP” (Extreme Pressure) oil this will ensure longevity of your gearbox. Typically, your drills will come from factory filled with:
- ISO EP320 Mineral Oil ... for PDD to PD50 including 2 Speed drives
- ISO EP320 Synthetic oil ... for SD, MD, UD, XD drives
Note : if unsure please contact the Digga Service department for guidance
Can I fit HALO on a competitor's earth drill?
You can't use the Digga HALO system on non-Digga earth drills because the HALO system is specifically designed and engineered to suit Digga earth drills.
Here are some key reasons:
- Compatibility: The HALO alignment system is built to integrate seamlessly with Digga drills, ensuring correct fitment and performance. Competitor earth drills may have different dimensions, or operational requirements that aren't compatible with the HALO system.
- Calibration: HALO uses 6 sensors to provide real-time feedback on the auger’s angle for precise drilling. These sensors are calibrated to work specifically with Digga’s drills and control systems.
- Warranty and Support: Digga products, including the HALO system, are covered under specific warranties when used with compatible Digga components. Installing HALO on a non-Digga drive will void warranties,
Still got questions?
We’re here to help. Whether you have general enquiries, questions about our product range, want to find your nearest dealer, or are ready to order – contact us today.
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