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Auger drill bit buying guide

Updated: 22 October 2026

You want a powered hole, and amazon.co.uk has put a joist bit, a bulb spiral and a two-handle fence-post machine in the same list. This auger drill bit buying guide puts the decision in order: the material first, then a diameter and a depth you can clear, then the shank and the drill. Bits in this set run from about £7.99 to about £23.99. The Einhell GP-EA 18/150 is about £148.45 without a battery. Prices and the full table stay on the [auger drill comparison](/hub/drilling-and-accessories/auger-drill). Those listings were checked on 19 October 2026. We did not drill a test hole. A qualifying purchase can earn a commission at no extra cost to you.

You want a powered hole, and amazon.co.uk has put a joist bit, a bulb spiral and a two-handle fence-post machine in the same list.

Our top picks

Einhell Einhell GP-EA 18/150 cordless earth auger

Best overall

Einhell Einhell GP-EA 18/150 cordless earth auger
9.2/10about £148.45
View offer
hsawbit hsawbit 40 mm x 230 mm wood auger

Alternative

hsawbit hsawbit 40 mm x 230 mm wood auger
9.2/10about £14.99
View offer
WORKPRO WORKPRO green set, 4 x 22 cm and 8 x 30 cm

Best value

WORKPRO WORKPRO green set, 4 x 22 cm and 8 x 30 cm
9.0/10about £13.99
View offer
On this page
  1. 1.Timber, soil, or a machine
  2. 2.Diameter and a realistic depth
  3. 3.Shank, drill and what solo means
  4. 4.Conflicts you should see on the listing
  5. 5.Which buy follows which job

Timber, soil, or a machine

The spiral is shaped for one material, so the first cut is timber, soil, or a machine that never goes in a chuck. The wood augers here are the hsawbit 40 mm by 230 mm at about £14.99 and the MOXPIFY 20 mm by 460 mm at about £15.99. The hsawbit listing says soft and hard wood, MDF, plywood and landscape timber, and it says not for metal. Garden augers, including Thrink, WORKPRO, LYFETC and Insaga, are for bulbs and small posts. The Einhell is neither: it is an 18 V machine with its own 150 mm auger and two handles. A wood bit in soil packs its flight. A garden spiral is the wrong cutter in a joist. If you are still unsure which family you are in, stay with wood auger or earth auger before you compare diameters.

Diameter and a realistic depth

The longest number in the title is often the shaft, not the hole you will finish. The RHS says most bulbs want to sit at about two to three times the height of the bulb, measured to the shoulder. A 60 cm Thrink shaft does not mean a tulip goes down 60 cm. A 4 cm garden bit suits many bulbs. A 10 cm bit is already a wide, shallow hole, and it is not the 150 mm Einhell. Planting depth, once you are sure the hole is soil, is on auger drill for planting bulbs.
Einhell Einhell GP-EA 18/150 cordless earth auger

Testsieger

Einhell Einhell GP-EA 18/150 cordless earth auger
9.2/10about £148.45
View offer

Shank, drill and what solo means

Most garden bits here claim a 3/8 inch hex for a 3/8 inch or larger chuck. That is a fit claim, not a promise that every cordless drill will turn the bit in clay. WORKPRO suggests 18 V or higher and states 14 V cordless as a minimum. Fourteen volts may turn a narrow bit in damp, loose soil. It is a weak match for an 8 cm or 10 cm flight in compacted ground, where reviews say you need torque. Solo on the Einhell means no battery or charger in the box. Einhell recommends a 2.5 Ah Power X-Change pack or larger. Hammer mode and impact mode are the wrong setting.

Conflicts you should see on the listing

Three conflicts change what you should believe before you pay. Insaga’s title says 7.5 by 81 cm, a bullet says 3 inch diameter and 32 inch length, and the spec field says 24.89 mm. The LYFETC 5 by 80 cm title says a solid shaft, while reviews describe two screwed parts that can undo in reverse. Four WORKPRO ASINs share 4.4 from 6,370 reviews, so that count is one family signal. The green short set is about £13.99 and the black set of the same stated sizes is about £19.94. Conditional picks are on best auger drill bit.

Which buy follows which job

If the hole is timber, buy a wood auger and ignore the soil spirals. If the hole is a bulb or a small stake in soil you can work, buy a garden bit whose shank matches the chuck you own, and treat the shaft length as reach. If you need many holes near 150 mm and you already have an Einhell battery, the solo machine is the honest buy, after you add the pack.

Common questions

What diameter should you buy for bulbs rather than fence posts?
Start from the bulb, not from the longest bit in the search. A 30 mm Thrink or a 4 cm WORKPRO bit matches many bulbs and plugs if the soil will let the flight turn. A 10 cm bit is a wide hole for a small bulb, and the 150 mm Einhell is a fence-post auger.
Does a longer shaft mean a deeper hole in clay?
The shaft is only the reach you might use if the soil, the stones and the drill allow it. In clay, buyers of these bits describe a hole that still needs a spade, or a bit that stops on a hard spot. The long LYFETC is titled 80 cm and reviewed as happier in damp soil than in dry ground.
Will a 3/8 inch hex fit a normal cordless chuck?
A 3/8 inch hex is meant for a 3/8 inch or larger chuck, which is what WORKPRO, LYFETC and Insaga claim. It fits when the shank is actually that size and the jaws close on the flats. Thrink’s page disagrees with itself, and a reviewer says the end slips, so a title is not a measurement.
Is 14 V enough when the listing also says 18 V?
WORKPRO prints both: 18 V or higher suggested, and 14 V cordless as a minimum. Treat 18 V as the drill these wider bits were described around, especially the 8 cm and 9 cm flights. A 14 V drill may cope with a narrow bit in loose, damp soil for a few bulbs.
How do you tell a two-piece shaft before you buy?
Read the title against the reviews, and look for a join in the photos. The LYFETC 5 by 80 cm title says solid shaft. Reviews on that ASIN say two screwed parts that undo in reverse. A one-piece claim with a threaded coupler in the pictures is the warning, because reverse can leave the tip in the hole.
When is a solo machine the honest buy instead of a cheap bit?
Choose the Einhell when the hole is about 150 mm, you have a lot of them, and you already own an Einhell 18 V battery of about 2.5 Ah or more. Buyers report a run of fence posts in clay and a day of hedging on one charge. They also report stops on stone, and two units returned after a cut-out.

Related pages

How to use an auger drill

Auger drill

Best auger drill bit for joists, bulbs or fence posts

Auger drill for planting bulbs: depth, not shaft length

Wood auger or earth auger: timber, soil, or a machine

Sources

Public UK sources from the research digest, last checked on 19 October 2026. Shelf prices and star lines are the amazon.co.uk figures in the display file.

  1. HSE: PUWER overview (retrieved 19 October 2026)
  2. HSE: hand-arm vibration in tree work (retrieved 19 October 2026)
  3. HSE INDG480: hand-arm vibration (retrieved 19 October 2026)
  4. Control of Vibration at Work Regulations 2005 (retrieved 19 October 2026)
  5. Consumer Rights Act 2015 (retrieved 19 October 2026)
  6. Electrical Safety First: drills (retrieved 19 October 2026)
  7. RHS: planting bulbs (retrieved 19 October 2026)
  8. Einhell UK: GP-EA 18/150 Li BL Solo (retrieved 19 October 2026)