Auger bit sizes: ship augers, short bits and the metric ladder
An auger bit is the deep-hole wood borer: a self-feeding screw point pulls the bit in, and an open spiral flute lifts the chips out of holes too deep for a spade bit to clear. The size data lives in two separate worlds, imperial and metric, and most charts mix them badly. This page prints both ladders from manufacturer catalogs, with model numbers: the Milwaukee ship-auger lines that dominate the imperial market, the Irwin Speedbor lines, and Makita's metric ladder [1] [7] [10]. For how augers compare with spade bits, Forstner bits and hole saws, see our wood boring bits compared page.
Three things to know before reading the charts.
- Imperial ship augers span 3/8 to 1-1/2 inch at every 1/16 step. The long (18 inch) and short (6 inch) lines do not cover the same sizes: the short line starts at 3/4 [1].
- Shanks step up with diameter: Milwaukee uses 5/16 hex through 1/2 inch and 7/16 hex from 9/16 up, and publishes flute length separately from overall length (18 inch bit, 15 inch flute) [1] [3].
- Metric augers step by 2 mm, not by the 1/16 inch of the imperial ladder, so a 6 mm set hole and a 1/4 in hole are close but not identical; the full metric ladder is 6 to 24 mm [10].
The imperial ladder: Milwaukee ship augers
Two lines, both from Milwaukee's own accessory catalog and cross-checked against its product pages and dealer listings [1] [2] [3]. The 18-inch line is the electrician's and timber-framer's tool, eleven sizes covering every 1/16 step from 3/8 through 1 inch. The 6-inch line is the same geometry shortened for single members, and it starts at 3/4: below that diameter a short auger has little advantage over a spade bit [1] [5].
| Diameter | 18 in line (15 in flute) | Shank | 6 in line | Shank |
|---|---|---|---|---|
| 3/8 in | 48-13-5500 | 5/16 in hex | not made | |
| 7/16 in | 48-13-5520 | 5/16 in hex | not made | |
| 1/2 in | 48-13-5540 | 5/16 in hex | not made | |
| 9/16 in | 48-13-5560 | 7/16 in hex | not made | |
| 5/8 in | 48-13-5620 | 7/16 in hex | not made | |
| 11/16 in | 48-13-5680 | 7/16 in hex | not made | |
| 3/4 in | 48-13-5750 | 7/16 in hex | 48-13-0753 | 7/16 in hex |
| 13/16 in | 48-13-5810 | 7/16 in hex | 48-13-0813 | 7/16 in hex |
| 7/8 in | 48-13-5870 | 7/16 in hex | 48-13-0873 | 7/16 in hex |
| 15/16 in | 48-13-5930 | 7/16 in hex | 48-13-0933 | 7/16 in hex |
| 1 in | 48-13-6000 | 7/16 in hex | 48-13-1003 | 7/16 in hex |
| 1-1/16 in | not made | 48-13-1063 | 7/16 in hex | |
| 1-1/8 in | not made | 48-13-1123 | 7/16 in hex | |
| 1-1/4 in | not made | 48-13-1253 | 7/16 in hex | |
| 1-3/8 in | not made | 48-13-1373 | 7/16 in hex | |
| 1-1/2 in | not made | 48-13-1503 | 7/16 in hex |
Read the flute, not the overall length, when you are planning a deep hole: Milwaukee's 1/2 x 18 bit (48-13-5540) is 18 inches overall with a 15-inch flute and a 5/16-inch hex shank, per its own spec page [3] [4]. One dealer table lists a 7/16 shank on this exact part number [5]; that is a feed error, and the manufacturer catalog wins: 5/16 through 1/2 inch diameters, 7/16 from 9/16 up [1]. The shanks are impact-rated, which is why these bits also appear in lineman's impact drivers [3].
Six-inch speed-feed cousins. Alongside the ship augers, Milwaukee's catalog lists the 6-1/2-inch Speed Feed bits at 5/8, 3/4, 7/8, 1 and 1-1/4 inch on 1/4-inch hex shanks, the fast clean-wood borers, plus the 1 x 6-1/2 auger 48-13-1000 with a 4-inch useable length [1] [2]. Same diameters, different job: speed feeds are for many shallow holes, ship augers for few deep ones.
Irwin: Speedbor Supreme and the classic lines
Irwin sells three relevant families. The current Speedbor Supreme ship augers (IWAX prefix) are bi-metal, 18 inches long, and take a 3/8-inch quick-change hex; the 3/4 x 18 (IWAX3008) is the reference size, with a re-sharpenable blade and a black-oxide finish, claimed by Irwin to last three times longer than its legacy equivalent [6] [7]. The legacy WeldTec ship augers cover 3/8 to 1-1/2 inch at the traditional 7-1/2 and 17-inch lengths, with a welded cutting edge for nail-embedded wood [8]. And the solid-center shorter augers come as a 6-piece pouch set containing exactly 1/4, 3/8, 1/2, 5/8, 3/4 and 1 inch [8]: note that set skips every odd 1/16 size, the same trap as the spade-bit sets [9].
| Family | Diameters | Lengths | Shank |
|---|---|---|---|
| Speedbor Supreme (IWAX) | 3/8 to 1 in, 18 in long | 18 in | 3/8 in quick-change hex |
| Ship auger, legacy WeldTec | 3/8 to 1-1/2 in | 7-1/2 and 17 in | varies by size |
| Solid center auger set 49998 (6 pc) | 1/4, 3/8, 1/2, 5/8, 3/4, 1 in | 7-1/2 in class | 5/16 in hex |
The Supreme and legacy lines do not share shanks, so check the hex size before mixing extensions: a 3/8 quick-change holder will not grip the older bits [6] [8].
The metric ladder: Makita wood augers
Metric augers step by 2 mm, and Makita's standard line is the cleanest example: ten sizes from 6 to 24 mm, all 200 mm overall with a 130 mm working length, straight shank [10] [11]. The same diameters also ship on 1/4-inch hex shanks in longer bodies: 250 mm (180 mm working), plus 400 and 450 mm reaches for thick timber and pole work [11] [12].
| Diameter | Part number | Overall length | Working length |
|---|---|---|---|
| 6 mm | D-07238 | 200 mm | 130 mm |
| 8 mm | D-07244 | 200 mm | 130 mm |
| 10 mm | D-07250 | 200 mm | 130 mm |
| 12 mm | D-07266 | 200 mm | 130 mm |
| 14 mm | D-07272 | 200 mm | 130 mm |
| 16 mm | D-07288 | 200 mm | 130 mm |
| 18 mm | D-07294 | 200 mm | 130 mm |
| 20 mm | D-07303 | 200 mm | 130 mm |
| 22 mm | D-07319 | 200 mm | 130 mm |
| 24 mm | D-07325 | 200 mm | 130 mm |
Cross-checking the two ladders: 6 mm is a hair under 1/4 in, 13 mm sits between 1/2 and 9/16 in, and 24 mm is a hair under 1 inch. Metric auger sets pair naturally with European cabinet hardware; imperial ship augers pair with North American framing and cable work. If a hole spec is given in one system, buy the bit in that system rather than converting, because the nearest size is often a few tenths of a millimeter off [10] [1].
Deep holes, nail-embedded wood, and what augers are not for
The screw point that self-feeds also means an auger wants a low-speed, high-torque drill: these are hole-hawg-class bits, not high-RPM tools, and the 1/2-inch-chuck minimum on Milwaukee's own product page is the tell [2]. For boring through old framing with hidden fasteners, both Milwaukee and Irwin sell nail-rated versions, Milwaukee's through-center cutting design and Irwin's WeldTec welded edge; both manufacturers publish nail-strike life claims on their product pages, and both charge accordingly [3] [6]. What an auger is not for: flat-bottomed holes (that is a Forstner bit), holes above 1-1/2 inch in wood (that is a hole saw), and shallow rough holes where a spade bit is faster and cheaper [9]. For running cable through finished walls rather than open framing, the long flexible bits are covered on our bell hanger and installer bit sizes page.
Choosing by hole, not by habit
Most auger work is cable and pipe clearings through framing: 1/2, 3/4 and 1 inch cover the great majority, which is why every maker's set concentrates there [8]. Buy the 18-inch length only when you actually bore through thick assemblies; the 6-inch bits drill the same holes in single members with less deflection. Above 1 inch, sizes exist (1-1/16 through 1-1/2 on the Milwaukee short line) but appear in no set, so a deep large hole usually means buying the individual bit [1]. For the pilot and screw holes around the same carpentry, see the pilot hole chart; for speeds by diameter across bit types, the drill speed chart.
Related pages
- Wood boring bits compared: spade vs Forstner vs hole saw, where the auger sits
- Spade bit sizes: the 17-size standard ladder and set contents
- Bell hanger and installer bit sizes: wire-pulling bits, stiff and flexible
- Drill bits by material: which bit family for wood, metal, concrete, tile
- Pilot hole chart: screw pilot sizes before any boring
Sources
- Milwaukee Tool accessory catalog (drilling section PDF): ship auger 18-in line 48-13-5500 through 48-13-6000 with shank steps (5/16 hex 3/8 to 1/2 in, 7/16 hex 9/16 to 1 in), 6-in line 48-13-0753 through 48-13-1503, Speed Feed 6-1/2-in line: milwaukeetool.com catalog (stateelectric mirror)
- Milwaukee Tool, 1 in x 6-1/2 in Auger Bit 48-13-1000 product page (useable length 4 in, double wing spurs, impact rated, 1/2 in minimum chuck): milwaukeetool.com
- Milwaukee 48-13-5540 spec pages at industrial distributors: 1/2 in diameter, 18 in overall, 15 in flute, 5/16 in hex shank, HSS, impact rated: franklinempire.com
- Construction Tool Warehouse, Milwaukee 48-13-5540 listing: diameter 1/2 in, overall length 18 in, flute length 15 in, shank 5/16 in quick-change hex: constructiontoolwarehouse.com
- National Supply Network listing carrying a 7/16 in shank on 48-13-5540 (the outlier this page corrects against the manufacturer catalog and two 5/16-spec distributors): nationalsupplynetwork.com
- Irwin IWAX3008 Speedbor Supreme 3/4 x 18 product listing with manufacturer specifications (bi-metal, 3/8 in quick-change hex, re-sharpenable blade, black oxide): toolup.com
- Weldesign Hardware, Irwin Speedbor Supreme IWAX3008 listing corroborating the same manufacturer spec block: weldesign.ca
- Irwin Wood Drilling catalog PDF: WeldTec ship auger line 3/8 to 1-1/2 in at 7-1/2 and 17 in, welded cutting edge for nail-embedded wood; solid center 6-piece pouch set 49998 contents 1/4, 3/8, 1/2, 5/8, 3/4, 1 in: Irwin catalog (unilog mirror)
- Irwin Tools, Ship Auger Bits product family page (wide flutes, fully forged, aggressive screw pitch, nail-embedded wood): irwintools.com
- Makita New Zealand accessory catalog, ship auger bits straight shank: D-07238 through D-07325, diameters 6 to 24 mm, 200 mm overall, 130 mm working length: makita.co.nz
- Makita UK, auger drill bits category: hex-shank wood augers 6 to 12 mm at 200 and 250 mm, plus 400 and 450 mm long versions with working lengths 330 and 380 mm: makitauk.com
- Makita Denmark, D-07238 product page (200 mm total length, 130 mm working length, EAN 0088381178792), corroborated by Australian retailer listing: makita.dk and alltoolsburleigh.com.au