The earth auger, often called a post hole digger, uses a rotating spiral blade to remove soil, creating a deep, cylindrical hole. When facing subterranean obstacles, the auger’s performance depends heavily on the size of the root encountered. While an auger can cut through smaller roots, larger, woody obstructions will halt the process, often resulting in sudden, powerful resistance.
Root Diameter and Auger Power
The primary factor determining if an auger can cut through a root is the root’s diameter and the torque of the auger’s powerhead. Most consumer-grade one-person power augers handle fine roots or those up to approximately 1 inch in diameter. Once the root diameter exceeds 1.5 to 2 inches, the mechanical resistance often surpasses the torque capacity of a standard power auger, causing it to bind or stall.
Hand augers, which rely on manual force, are limited to cutting roots no thicker than about 3/8 of an inch (1 centimeter). More powerful two-person augers or hydraulic models mounted on machinery can handle thicker roots due to their higher torque and robust construction. However, even these heavy-duty machines can be stopped by a major structural root.
The design and sharpness of the auger blade also play a significant role in cutting efficiency. Blades with aggressive, serrated edges or specialized carbide tips are more effective at slicing through tough, fibrous root material than standard, straight-edge blades. A dull blade will tend to wrap the root around the shaft or bind completely instead of cleanly severing the material, regardless of the auger’s power.
Operational Techniques for Managing Small Roots
To successfully navigate areas with small, manageable roots, operators should use a controlled technique that allows the blade to cut rather than impact the obstruction. Begin drilling at a moderate speed and apply steady, downward pressure, giving the cutting edge time to shave the root material away gradually. This slow approach is more effective than sudden, forceful drilling, which increases the likelihood of binding.
Employing an oscillating or “pumping” motion can also help when resistance is encountered. This involves raising the auger slightly, then lowering it back down in a short, repetitive cycle to expose the root to a fresh part of the blade and clear away debris. The continual lifting helps dislodge cut fragments and prevents the auger flights from becoming clogged with soil and root fibers.
Stopping frequently to clear the hole of debris is important to maintain cutting efficiency. Accumulation of soil, especially sticky clay or wet material, can increase friction on the auger flights, reducing the power available for cutting roots. For dry or clay-heavy soil, introducing a small amount of water into the hole can act as a lubricant, making it easier for the auger to penetrate and clear material.
Contingency Plans for Large Root Obstacles
When the auger encounters a root too large to cut, the machine will bind instantly, posing a safety risk from kickback. Anti-kickback technology in some electric augers will cut power when the blade binds, but gas-powered models can violently twist the handles, potentially causing injury. The safest immediate action upon binding is to stop the motor and attempt to reverse the auger to free the bit.
If the obstruction cannot be cleared with the auger, manual intervention becomes necessary. The hole should be cleared of loose soil to expose the root, which can then be cut manually. Tools such as a sharp mattock, a small axe, or a reciprocating saw fitted with a wood-cutting or pruning blade are effective for severing larger roots.
After manually cutting the root, the auger can be reintroduced to clear the remaining soil and deepen the hole. If the root is too difficult to remove, adjusting the planned hole location is the most practical alternative. Moving the hole just a few inches often allows the auger to bypass the major structural root entirely, permitting the project to continue without excessive effort.