Why Do I Need an Earth Auger?
An earth auger works like a power drill, using a large bit to quickly bore a hole into the ground.
- One of the most common uses for an auger is installing fence posts. People often call these machines post hole augers or fence post augers. If you’re installing a fence, digging post holes with a power earth auger will save you a lot of time and effort compared to digging with a post hole digger.
- Deck installations are easier with the efficiency of a power auger as well; you can dig footings for the deck posts in a matter of minutes with a power auger.
- You can even find smaller bits that are perfect for quickly digging planting holes for a garden, shrubs or trees.
- Some small, flexible auger bits fit a power drill, allowing you to bore holes to run cable under sidewalks and driveways.
Our power auger how-to will show you the steps for using an earth auger to dig post holes.
What Should You Look for When Buying An Auger?
When considering a power auger, pay attention to the two main components of the tool: the powerhead and the auger bit.
- Powerhead: The powerhead includes the engine or motor and drive mechanism of the auger tool. You’ll find smaller powerheads designed for use by one person. These are most common for do-it-yourself use. Larger, two-person powerheads are more powerful. They can drive larger bits to dig larger holes. These are typically for professional use, but you can often rent one for a larger DIY project.
- Auger Bit: Like a power drill twist bit, an earth auger bit has a series of flutes running around a central shaft. The flutes remove earth as the bit bores a hole. As with a drill bit and drill, the bit needs to fit the powerhead. Standard bits can dig holes to a depth of about 3 feet, but auger bit extensions let you dig an additional foot or two. Some larger auger bits have a blade attached to the flutes near the point. This auger bit blade cuts into the ground to allow the flutes to cut into the ground and begin removing soil.
Choose an auger based on the number, size and depth of the holes you need. Your soil type might also be a factor. If it’s rocky you’ll need a more powerful auger and a larger bit. Here are some factors to keep in mind.
- A one-person machine weighs about 35 pounds; a more powerful two-person unit is close to 60 pounds. This doesn't include the weight of the bit, which is likely to be about 15 pounds.
- A one-person auger is likely to run on a two-cycle engine, which requires a gas/oil mix. You can also find battery-powered one-person augers. Two-person models are generally four-cycle and need no fuel mixing.
- Even though a power auger can make your job easier, it still requires effort to move it around and to control it, particularly if it delivers a lot of torque or rotational force. It’s a good idea to have a helper to share the work even on a one-person machine.
If you just need an auger for one project and don’t want to purchase one, you may be able to rent an earth auger from your local Lowe’s.
Before beginning any excavation, call 811 to check for underground utilities.
What Size Auger Do You Need?
When considering auger size, you’re typically thinking about the size of the auger bit, and the hole size you need. The auger bit size you need — the diameter and length —depends on the work you’re doing.
For post holes, you need to consider the size of the posts you’re installing and the hole will need to be big enough to allow for fill material. While building codes may dictate post hole size and depth, you’ll generally want a post hole auger that can dig a hole up to three times the width of the post.
If you’re using an auger for planting, the hole size and auger size depend on the plant.
Auger Bit Diameter
Match the bit diameter to the hole size you need for your project.
- If you need to dig holes to set 4-by-4 posts for a mail box or fence, you’ll need an auger that can bore a 10- to 12-inch diameter hole. This allows for the post and well as the fill dirt or concrete to hold the post in place.
- A 6-by-6 post would need a fence post auger with a larger diameter bit — 12 inches or more.
- Smaller metal U- or T-posts for garden fencing or wire fencing would typically only need a 6-inch-diameter bit.
- A 2- to 4-inch auger bit can work well for boring planting holes for bulbs and seedlings.
- Larger quart and gallon potted plants, shrubs or trees require larger bits — from a 6-inch-diamteer auger for a quart potted plant up to a 12-inch bit for a 5-gallon potted tree.
Auger Bit Length
The auger length determines the depth of the holes you can dig.
- Local codes will dictate specifics, but as a general rule a post hole should have a depth between 1/2 and 1/3 of the above-ground height of the post.
- 36 inches or 3 feet is a standard length for an auger bit. For holes deeper than 3 feet, you’ll typically need a bit extension.
- For planting holes, depth will depend on the plant and, for trees and shrubs, the size of the root ball. The plant tag should give you planting tips.
Power Auger Safety
Follow the manufacturer's instructions for use and safety. Here are some general guidelines:
- Hearing and eye protection are a must. Dirt will fly as you clear the hole, so also wear sturdy shoes and long pants.
- Turn off the machine when moving to the next hole.
- Tree roots and rocks can stop a bit in an instant, so be prepared for the unexpected jolt.
- Landscape fabric can quickly get wrapped around an auger bit and even cause injury. Know what’s under the surface where you’re digging.
- If you’re not setting posts the same day, cover the holes with something (e.g., a piece of wood) to prevent debris from getting in or people or pets stepping or falling in.
- Fuel, clean and maintain the machine according to the manufacturer's guidelines.
What Is the Life Expectancy of an Auger?
How long an auger lasts depends on a variety of factors, including:
- How Often You Use the Tool: More use will add wear to the power head and bit.
- The Power the Auger Can Deliver: More powerful auger tools can handle larger holes and more digging.
- Soil Type: Heavier, rocky soil can increase the wear on an auger, particularly if it’s underpowered for the work.
- Maintenance: Follow the manufacturer’s instructions for use and maintenance to get the best life from an auger.
You can find replacement blades for some auger bits, allowing you to keep a sharp blade on the bit to minimize wear on the powerhead.
Ice Augers
Earth augers aren't ice augers. Ice fishermen need a power head that’s designed to start and run in cold weather. More importantly, an ice auger bit is vastly different from an earth auger. Ice bits are extremely sharp to cleanly penetrate thick ice.