The right auger depends on whether the soil will stay on it on the way up: a bucket auger, a closed cylinder with a cutting edge at the bottom, holds loose, crumbly or damp soil and works well in clay; a spiral auger carries firm, cohesive soil up on its flights but loses sand and clogs in wet clay; and an open-sided clay auger can be scraped clean of sticky clay. Match the auger to what each load does when you pull it, and change auger when the soil changes.
Part of Deep Wells
Auger types are the hand-boring tools used on a rod string, differing in how they cut the soil and how they hold it while being lifted. The Deep Wells guide uses a bucket auger for clay and a spiral auger for mixed soils.
Each Shape Solves One Problem And Causes Another
| Auger | How it holds the soil | Works in | Fails in |
|---|---|---|---|
| Bucket | A closed cylinder with cutting lips at the base; soil is pushed in and kept by the walls | Clay and damp, crumbly or loose soil; the standard for clay in the Deep Wells guide | Dry sand that runs out; very hard or stony ground |
| Spiral (helical) | Soil rides up on the flights | Firm, cohesive soils and mixed soils, above water | Loose sand, which falls off the flights; wet clay, which clogs the flights |
| Clay | An open shell or spoon shape cut so the clay can be pushed out or scraped off | Sticky, plastic clay that clings to a closed bucket | Loose dry soil, which falls out of the gaps |
These are working categories, not fixed names; one place calls a tool a bucket auger and another an Edelman or a gouge. Judge by what comes up in the load. A tool that always comes up empty of loose soil needs walls; one that comes up packed solid and has to be chiselled clean needs an open shape.
What You Need
- At least two augers of different types — a bucket auger and a spiral auger cover most soils
- A rod string and T-handle — see Extension Rods
- A scraper and a bucket of water — to clean sticky clay off the tool
- Steel plate and pipe to make or repair augers, if none are salvaged
- A tape or marked rod — to measure the diameter of the hole against the casing
Method: Choose, Try, Change
Step 1: Start with the bucket. Begin with the bucket auger in most soils; it is the most forgiving.
Step 2: Watch what comes up. If the load slides out as the auger leaves the hole, you need a closed bucket. If the auger comes up solid with clay, use a clay auger or scrape the bucket clean each trip.
Step 3: Try the spiral in firm ground. In firm, mixed soil above the water table, a spiral auger can fill and clear faster than a bucket. If it comes up clean and empty it is wrong for that layer.
Step 4: Switch at the water. When sand turns wet and runs, stop augering and bail (Bailer Operation).
Step 5: Keep the edges sharp. A dull cutting lip makes the work much harder. Dress it with a file when it rounds over.
Worked Example: Hole Diameter And Effort
An auger bores a hole as wide as itself, and the area it cuts grows with the square of the diameter. Going from a 10 cm to a 15 cm auger multiplies the cut area by (15 ÷ 10)² = 2.25, so the soil per metre of hole rises from π ÷ 4 × 0.10² × 1 m = 7.9 L to π ÷ 4 × 0.15² × 1 m = 17.7 L. The effort rises by a similar factor. If the hole must take casing and a gravel pack, bore a narrow pilot hole first and open it up in steps (Percussion Drilling works out the casing clearance).
Common Mistakes
- One auger for every soil. The wrong shape wastes hours.
- Forcing a spiral through wet clay. It clogs and may jam.
- Ignoring the diameter. An auger that cannot take casing is only good for a test hole.
- Leaving clay on the cutting lips. Clean the tool every trip.
Safety
A turning tool and a cutting edge
Keep hands clear of the cutting lips and the flights when the rods are turning or lifted. A pinched finger or an auger dropped down the hole can injure and ruin the work, so lift the string with a hoist or several people, and cover the hole when the work stops (Augering).
What’s Next
- Learn next: Extension Rods — joining the string
- Combine with: Well Casing — sizing the hole to the casing