Earth augers for excavators – choose the right diameter, length and material
What is an earth auger?
An earth auger is a screw-shaped drilling attachment that is mounted on an earth auger drive and rotated by hydraulic power to drill circular holes in the ground. Earth augers are available in diameters from 100 mm to 1,500 mm.
Applications
- Ground and civil engineering works – Holes for fence posts, signposts, lighting poles
- Garden and park – Planting holes for trees and bushes
- Construction sites – Holes for foundation piers and micropiles
- Geothermal and wells – Vertical holes for ground source heat pump systems
Professional civil engineers report up to 80% time reduction in post setting compared to manual digging.
Earth auger types by ground type
- Standard earth auger – Loose to semi-solid soil (topsoil, clay, till).
- Rock Auger – Tungsten Carbide cutters for rock-mixed ground and rocky soil.
- Frost Auger – Hardened cutters for drilling in frozen ground.
- Fishtail Auger – V-shaped cutters, effective for loose soil and sand.
Choosing the right diameter
- 100–150 mm – Fence posts, drainage pipes, electrical installations
- 200–300 mm – Garden planting (bushes), road signs
- 400–600 mm – Trees (trunk diameter 10–20 cm), lighting poles
- 800–1,200 mm – Large trees, power line poles, large foundation piers
Rule: The diameter of the bore hole should be 1.5–2 times the diameter of the post or root ball.
Frequently asked questions
How deep can you drill with an earth auger?
With extension sections, you can reach 4–6 meters deep.
How much does an earth auger cost?
A standard earth auger for mini excavators (150–300 mm diameter) typically costs 3,000–8,000 SEK.
Can I drill in clay with a standard auger?
Yes, but dense clay can get stuck in the spiral screw. Choose an earth auger drive with high torque and clay removal cutters.
How do I maintain my earth auger?
Clean after each use, check the pilot tip and Tungsten Carbide cutting edges for wear regularly.