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.