Spade bit vs auger
Updated: 2026-10-23
You are about to bore timber thicker than the bit looks, and the pouch holds a flat wood bit about 150 mm long. A paddle is fast when you can reach the exit and clear the chips. An auger pulls chips out of a deep bore. The [spade bit comparison](/hub/drilling-and-accessories/spade-bit) does not stock augers and does not rank the twelve flat bits against them. There is no auger price on this page. The zone the hole must sit in does not change with the tool.
You are about to bore timber thicker than the bit looks, and the pouch holds a flat wood bit about 150 mm long. A paddle is fast when you can reach the exit and clear the chips. An auger pulls chips out of a deep bore.
You are about to bore timber thicker than the bit looks, and the pouch holds a flat wood bit about 150 mm long. A paddle is fast when you can reach the exit and clear the chips. An auger pulls chips out of a deep bore. The spade bit comparison does not stock augers and does not rank the twelve flat bits against them. There is no auger price on this page. The zone the hole must sit in does not change with the tool.
Our top picks
| Badge | Product | Format | Extension | Stated diameters | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Bosch Bosch Expert SelfCut Speed set | Self-feeding set | 152 mm, included | 16, 18, 20, 22, 25, 32 mm | 7.2 | about £22.50 | View offer |
 SHALL SHALL 8-piece spade bit set | Set | No | 6, 10, 13, 16, 19, 22, 25, 32 mm | 8.1 | about £10.99 | View offer | |
| Best value |  Gunpla Gunpla 6-piece spade bit set | Set | No | 10, 12, 16, 18, 20, 25 mm | 7.3 | about £6.98 | View offer |
On this page
What each bit is for
A spade bit is a flat blade, a centre point and two lips, usually 150 mm or 152 mm overall here. You push a plain paddle. It cuts quickly in softwood, chipboard and ply, and the hole is functional rather than finished. That is a stud, a lock, or a first-fix hole you can see through, in rotation only.
An auger is a screw tip with a spiral flute. The screw draws the bit in and the flute carries chips out. It is the deeper option once you are past the short working length of a flat bit. Overall length includes the shank. Buy the shortest auger that still reaches.
The spade is the smaller, quicker tool in thin timber. It fails when the chips have nowhere to go: the bit rubs, the timber burns, and the point stops steering. That is when an auger is the other tool.
Depth, wander, and a packed hole
You can withdraw and clear, and the how to use a spade bit page says when. Each restart can leave the axis, and a self-feeding tip pulls forward before you see the bend. Rotary-hammer mode is the wrong fix.
A 152 mm extension, on the Bosch set and in the BULLITT title, reaches a ceiling void. The joint can loosen, and the head is still flat. Longer Bosch spades on the manufacturer page are not rows here.
If you cannot see the point break through, a paddle is guessing. Clamp either way: an auger screw will also snatch loose work. The Bosch bullets here exclude hardwood. Silence does not turn a paddle into an auger.
A threaded spade is still a spade
Bosch Expert SelfCut Speed has a threaded tip on a flat blade. Reviews call it fast and a grab. It does not lift chips the way an auger flute does. The 3× line is only against Bosch bit 2609255269. Use light pressure, because the thread is already feeding.
BULLITT’s threaded tip is in the reviews, not in the specification table. Those texts call the cut fast but rough. A threaded spade in a deep joist pulls harder while the chips pack. If you are already backing a 32 mm Bosch bit out every few seconds with the extension fitted, this file’s flat bits are finished. A second bar is not a solution here.
Decide, then check the joist
Use the flat bit when the hole is short and reachable, in a diameter the listing states. Prefer an auger when the timber is thick or the chips pack however often you clear. Take the shortest auger that reaches. A hole saw is a shallow circle in thin sheet, not a deep joist.
The joist rules still apply: centre line, no more than a quarter of the depth, and not mid-span. A 32 mm auger removes the same timber as a 32 mm spade. The detail is on drilling holes in joists for cables.
If you stay with a spade, pick a row whose diameter fields agree. The Bosch single that says 25 mm and 40 mm is a bad deep-joist bet. The Bosch set is a flat bit with an extension, not an auger.
Common questions
When is a flat bit enough for a joist?
When it is one solid member, the hole is inside the quarter-depth zone, and you can reach the exit or clear chips before they pack. A run through several deep joists, where you cannot see the point come out, is an auger job.
When does an auger clear chips better?
When the hole is deeper than a flat blade can pack and still cut. The spiral lifts the waste. A spade leaves it in the bore until you pull the bit back. If the timber is still burning, the flute is what you are missing.
Is a Bosch self-feeding spade an auger?
No. The Expert tip is a thread on a flat blade. Those two listings are softwood and particleboard only. Chip clearance is still a paddle’s. The 3× line is against an older Bosch spade, not an auger. BULLITT’s threaded tip is only in reviews.
Will a 152 mm extension turn a spade bit into a deep-joist tool?
It makes a short bit reach further. The head is still flat, and the joint can loosen. It is a ceiling-void workaround, not an auger flute. Coupling extra bars is not a recommendation here.
Which one wanders less in thick timber?
The auger. The screw holds the centre while the flute keeps the hole clear. A packed spade stops steering. In thin, clamped board the difference is small, and the spade is the quicker cut.
Do I still have to follow the joist hole rules if I change bit?
Yes. The rules limit the timber you remove and where. A 32 mm auger mid-span is the same mistake as a 32 mm spade. I-joists and metal webs stay on the maker’s sheet.
Are hole saws a third option, and does this site compare augers?
A hole saw is for a wide, shallow hole in thin material, not a deep joist. This file has no auger ASIN. Auger models are a different comparison.
Related pages
Sources
Public UK sources last checked on 19 October 2026. Shelf prices, stars and review counts are the amazon.co.uk listings read on that date.
- CMT Group UK, drill bits for construction materials (retrieved 19 October 2026)
- BuildWiz UK, drill bits (retrieved 19 October 2026)
- LABC, notches and holes in solid timber joists (retrieved 19 October 2026)
- East Lindsey Guidance Note 15, notches and holes (retrieved 19 October 2026)
- Professional Electrician, notches and holes in joists (retrieved 19 October 2026)
- HSE CIS65, concealed cables (retrieved 19 October 2026)
- HSE INDG291, PUWER and drilling machines (retrieved 19 October 2026)
- Bosch Professional GB, Expert SelfCut Speed spade bits (retrieved 19 October 2026)