By Mike Hale
Whether you're installing street signs or fences, or planting shrubs, you'll have to dig a proper hole to do the job right. And while the process is far from rocket science, it's not quite as simple as one would expect. First, you must consider the soil structure that you'll dig into, as well as the depth, diameter, and number of holes to be dug. Next, you must select the proper tools to perform the work.
Advancements in drill designs and accessories have made what was once a simple hole digger into something much more — a complete solution for any digging project. Taking the time to learn about available options prior to selection ensures the success of a project on all levels — from safety and productivity to quality and return on investment.
Hydraulic vs. mechanical drills
Engine-powered, one-man earth drills are typically available in two styles: hydraulic and mechanical. While often similar in appearance, these two styles operate differently — with distinct features and options.
Hydraulically powered drills are built rugged and powerful for the most challenging digging projects, including those in more complex soil conditions, rough and rocky terrain, and even frozen ground. They offer controlled, precise operation at a higher torque, allowing operators to drill accurately in difficult applications. Hydraulic models also incorporate a reverse auger operation function. Should the auger become lodged under an object, such as a rock or tree root, it can be removed safely and easily by running the auger in reverse.
Generally accepting of larger diameter augers, these units are ideal for single-hole projects such as sign installation. Most are compatible with smaller augers as well, making them ideal for a variety of lawn and landscape projects.
Though versatile, hydraulic drills pose one distinct drawback. The tradeoff of controlled operation at a higher torque is slower operation, so they aren't the perfect solution for projects requiring multiple holes.
If you're looking for speed, mechanical drills are transmission-powered units that offer high-speed rotation for high productivity and clean holes. Compact, lightweight, and still packing a powerful punch, they're best-suited for use with smaller diameter augers and are ideal for projects calling for several narrow holes, such as fence and deck installations and decorative plantings.
Unlike hydraulic models, mechanical units don't have a reverse feature, which can present a problem if the auger becomes caught under an obstruction. The operator has to remove the in a counter-clockwise motion.
Augers: points and blades
An auger, or drill bit, usually includes a rotating helical screw blade called a flighting that acts as a screw conveyor to remove the drilled-out material. The auger's point and blade (commonly referred to as its tip) does the actual cutting as the unit rotates, and helps protect the auger's flighting from excessive wear. As important as the tip is to drilling success, it's imperative to know the available options and in what type of soil each performs best.
A standard, general-purpose point with a side-mount cutting blade works well in most conditions, particularly in sandy, loam-type soils and softer clays. General-purpose tips are compatible with most standard augers, in varying lengths and diameters.
When drilling in more solid, dense material such as limestone, sandstone, hard clay, or frozen ground, a carbide blade provides the best performance. Rather than digging into the material, the blade cuts the clay or ground into small pieces, allowing the operator to drill much faster. The blade mounts to the bottom of most standard augers and replaces the general-purpose point and cutting blade.
If the drilling task includes challenging conditions like loose, gravely, or rocky soil, a heavy-duty auger, point, and blade combination will tackle it best. Most effective when attached to low-speed drills like hydraulic units, it features a larger, more rugged and aggressive flighting than standard augers, and incorporates a special dirt-tooth blade in addition to a heavy-duty point.
EARTH DRILL SELECTION CHEAT SHEET
Ultimately, the drilling task will dictate which type of earth drill and auger size to use. Most manufacturers will offer several auger options for their drills, from the smallest model for applications like soil nursery work up to the largest augers commonly used in foundation repair or soil sampling.
Most earth drills are designed for easy transport; some include both front and rear handles for convenient loading and unloading. Mechanical units are generally the easiest to move, and can be loaded in a car trunk, the back of an SUV, or in a pickup truck bed. Hydraulic units are typically larger and a bit less convenient to move from site to site. But on the flip side, manufacturers offer a variety of transport modes for them, giving operators flexibility to match their vehicle and space needs.
The smallest hydraulic models are best moved with a pickup truck or small trailer. In cases where truck and trailer space is minimal, consider a model designed to be towed behind the vehicle, as it frees up valuable room for jobsite tools and other equipment.
If you're looking for yet another alternative, a hydraulic unit is now being offered that separates into two pieces, making the entire unit lighter and much more manageable. The power pack can be placed in the vehicle, while the rest of the drill is transported behind the vehicle and off the ground — eliminating common towing hassles. The unit's special hitch design is compatible with even small SU-Vs and pickups. The unit provides an option for those without a vehicle large enough to meet typical towing requirements, while still offering the benefit of freeing up precious vehicle space.
Digging into the ground can be dangerous. One-call phone numbers have been established for every area across the country to help protect operators and let them know what's below the surface before digging. But the drill itself can pose a safety threat to the operator too, making it crucial to look for units designed with added safety features.
Certain models incorporate the engine and auger into one piece, while some manufacturers offer a configuration that places the engine on a wheeled chassis, which sits back a few feet from the operation point. The separate mounting keeps harmful exhaust emissions at a distance, and may also protect the operator in other ways.
Some models with a separate engine chassis utilize a steel torque tube that transfers digging torque from the drill head to the engine carriage. This allows operators to use larger diameter augers without fear of dangerous kickback. Additionally, the torque tube enhances drilling ease and reduces operator fatigue. A more alert, less fatigued operator is more likely to pay attention and handle the drill properly. Easier operation also reduces physical stress, including back problems and muscle strain.
Hydraulic units often feature a pressure relief valve. If the auger becomes overworked and the drill reaches a certain hydraulic pressure, the valve releases to stop the auger's rotation. This halts the drill before it reaches a point where it stops the engine or causes damage to the machine.
Mechanical units are also built with unique safety features, such as a centrifugal clutch. If the drill encounters a buried object or the auger is overloaded, the clutch automatically slips, protecting the operator from serious injury. This also eliminates potential damage to the drive cable and transmission gears, reducing the likelihood of expensive repairs or full replacement.
Both experienced operators and first-time hole-diggers want a machine that's easy to use. An ergonomic design provides a more comfortable, user-friendly experience.
Look for large, easy-to-grip handles for better control and more comfortable operation. Also look for a model that places operator controls right on, or in close proximity to, the handle. Functions such as a hydraulic unit's forward/reverse switch should be adjacent to the machine's on/off switch for added convenience.
Choosing a unit with a high-quality engine is a must, as a drill's operation is greatly dependent on its engine. Look for one from a reputable manufacturer that includes a warranty and adequate service network. For portable units with a separate chassis for the engine, look for a durable, steel frame that will help protect the engine and its components.
To ensure the machine is safe for even the most delicate lawns and turfs, consider a unit with large, pneumatic or semi-pneumatic tires. The benefit is two-fold: quality tires won't damage turf, and they allow the unit to easily traverse a variety of terrain conditions.
Look for a manufacturer that provides multiple auger tips, as well as augers in multiple lengths and diameters. Some manufacturers offer snap-on augers, making the change-out process quick and easy, and eliminating the need for extra tools. Snap-on auger extensions offer the ability to achieve various digging depths without requiring multiple augers, adding versatility and saving money.
Finally, an earth drill that's easy to care for is ideal. In the event the machine becomes damaged, you'll find that a unit that can be serviced in the field without special tools is most convenient.
As an added bonus, a drill that's easy to maintain will encourage the operator to stick to a routine maintenance schedule, preventing future issues, enhancing longevity, and ultimately maximizing your return on investment.
Hale (firstname.lastname@example.org) is sales manager for earth drill and auger manufacturer Little Beaver Inc., headquartered in Livingston, Texas.