Buy M12 Bolts Online in Australia
M12 is one of the most common metric bolt sizes used across Australian construction, structural steel, agriculture and general engineering. AIMS stocks M12 bolts in hex bolt, hex bolt & nut, cup head, purlin, U-bolt and L-bolt (foundation bolt) styles, across grades 4.6, 8.8 and 10.9 mild/high-tensile steel plus 304 (A2) and 316 (A4) stainless, in plain, zinc-plated, hot-dip galvanised and nylon finishes. If you need a length, grade or finish you can't see below, give our team a call — most of our range extends well beyond what's listed online. Not sure which one suits your job? Our Hex Bolt Guide: Types, Sizes & How to Choose covers selection in detail.
M12 Bolt Quick Reference
| Nominal diameter | 12mm |
| Thread pitch | 1.75mm coarse (standard); 1.25mm or 1.5mm fine on selected lines |
| Head across flats (AF) | 19mm spanner/socket — hex head and hex flange styles only |
| Grades/classes stocked | 4.6, 8.8, 10.9, 304 stainless (A2), 316 stainless (A4) |
| Finishes stocked | Plain, zinc plated, hot-dip galvanised, natural nylon, bare stainless |
| Head/style types | Hex bolt, hex bolt & nut, cup head bolt & nut, purlin bolt & nut, U-bolt, L-bolt (foundation bolt) |
| Length range | 20mm to 600mm, depending on style and grade (see below) |
| Brands stocked | Hobson, Inox World, Bumax, Bremick |
M12 Bolt Types Stocked at AIMS
Hex Bolts & Hex Set Bolts
Our core M12 hex bolt range runs from grade 4.6 mild steel through to 8.8 and 10.9 high tensile, in plain, zinc-plated and hot-dip galvanised finishes from Hobson, plus 304 and 316 stainless steel hex bolts from Inox World and Bumax's 8.8 and 10.9 stainless high-tensile range. Standard coarse-thread (1.75mm pitch) hex bolts run roughly 20–200mm, and we also stock a Metric Fine Hex Bolt Class 8.8 line with 1.25mm and 1.5mm fine pitch options for applications that call for finer thread engagement. A natural nylon M12 hex bolt (DIN 931) is available where a fully non-metallic, non-conductive fastener is needed.
Hex Bolt & Nut Sets
Hex bolts are also available pre-paired with a matching nut across 4.6 and 8.8 grades, in plain, zinc-plated and hot-dip galvanised finishes — including an extra-long "XL thread" 4.6 hot-dip galvanised line running out to 220mm, and a standard 4.6 galvanised set that extends all the way to 600mm for longer through-bolt jobs.
Cup Head Bolts & Nuts
Cup head (dome head, square neck) M12 bolts are stocked in grade 4.6 plain, zinc-plated and hot-dip galvanised finishes and Class 8.8 hot-dip galvanised, plus a 316 stainless steel cup head square neck bolt from Inox World. Cup head bolts don't take a spanner — the square neck seats into the timber or steel to stop the bolt spinning while the nut is tightened — so these are the pick for timber-to-steel and rural fencing/gate connections where a flush, tamper-resistant head is wanted. Lengths run from 30mm up to 500mm on the longer plain-finish line.
Purlin Bolts & Nuts
M12 purlin bolt & nut kits (including a hex flange bolt & nut and a bolt/nut/washer kit from Hobson, and a purlin flange bolt & nut kit and purlin bolt & nut assembly from Bremick) are stocked in Class 8.8 zinc-plated and hot-dip galvanised, and grade 4.6 zinc finishes, for fixing purlins and girts to structural steel.
U-Bolts
Our M12 round U-bolt kit (Hobson, mild steel, hot-dip galvanised) is stocked across seven bend sizes, from 65/76mm up to 150/168mm, for pipe, conduit and round-section mounting and clamping jobs.
L-Bolts (Foundation Bolts)
The Hobcast Foundation L-Bolt (Hobson, mild steel, hot-dip galvanised) is available at M12 in 300mm, 350mm, 400mm and 450mm lengths for anchoring base plates and structural steel into concrete.
Grades, Materials & Finishes Explained
Grade 4.6 is a mild steel bolt suited to general, lower-load fixing. Grade 8.8 is high-tensile steel and the default choice for most structural, automotive and mechanical fixing where higher clamping load and shear strength matter. Grade 10.9 steps up again for the most demanding load cases. 304 stainless (A2) suits general corrosion resistance indoors and in most outdoor settings; 316 stainless (A4) adds molybdenum for better resistance to chlorides and is the better pick near the coast, in marine environments, or around washdown and chemical exposure. Bumax stainless bolts combine 316-grade corrosion resistance with a genuine 8.8 or 10.9 high-tensile rating, for jobs where you need both. On finish: zinc plating suits indoor or low-exposure use, hot-dip galvanising is the standard for outdoor and structural steel work, and plain (uncoated) finish is typically specified where the bolt will be painted or isn't exposed to weather.
Companion Collections
Looking for a different size, or the full bolt range? Check out:
- Bolts — the full AIMS bolt range across all sizes and styles
- Hex Bolts — hex head bolts across all metric sizes
- Hex Bolts & Nuts — bolt and nut sets across all sizes
- Cup Head Bolts & Nuts — dome head bolts across all sizes
- Purlin Bolts & Nuts — purlin fixing kits across all sizes
- U-Bolts — round and square U-bolts across all sizes
Order M12 Bolts from AIMS
Not sure which grade, finish or head type is right for your job? Our team can help you match the right M12 bolt to the application — call us on (02) 9773 0122, get in touch via our contact page, or request a quote for bulk or trade pricing. We're an Australian-owned business and we're genuinely happy to talk through the detail.
Frequently Asked Questions
What is the M12 bolt size?
An M12 bolt has a 12mm nominal shaft diameter and a 1.75mm coarse thread pitch (some lines are available in 1.25mm or 1.5mm fine pitch). A standard M12 hex bolt takes a 19mm spanner or socket across the flats.
Are M12 bolts 12mm?
Yes — the "12" in M12 refers to the nominal outside diameter of the bolt's threaded shaft in millimetres, not the head or spanner size.
What size spanner or socket fits an M12 bolt?
A standard M12 hex head or hex flange bolt takes a 19mm spanner or socket across the flats. This applies to hex-drive heads only — cup head bolts, U-bolts and L-bolts don't have a spanner drive; cup head bolts are tightened from the nut end while the square neck holds the bolt still.
What's the difference between coarse and fine thread M12 bolts?
Standard M12 bolts use a 1.75mm coarse thread pitch. AIMS also stocks a Metric Fine Hex Bolt Class 8.8 line in 1.25mm and 1.5mm fine pitch, which gives finer thread engagement and is sometimes specified for higher-vibration applications or where a finer adjustment is needed.
What grade M12 bolt should I use?
It depends on the load and environment. Grade 4.6 mild steel suits general, lower-stress fixing. Grade 8.8 high tensile is the standard choice for most structural and mechanical applications. Grade 10.9 is for higher-load jobs. For corrosion resistance, 304 stainless suits general outdoor use and 316 stainless is the better choice near the coast or in marine/chemical environments.
Do M12 bolts come with a nut included?
Many of our M12 lines are sold as bolt & nut sets — including hex bolt & nut, cup head bolt & nut, purlin bolt & nut kits and U-bolt kits. Standard hex bolts and hex set bolts are sold as the bolt only.
What lengths do M12 bolts come in?
It varies by style. Standard M12 hex bolts run roughly 20–200mm. Hex bolt & nut sets extend out to 600mm on our longest galvanised line. Cup head bolts run 30–500mm. L-bolts (foundation bolts) are stocked at 300, 350, 400 and 450mm. Check the specific product page for the exact lengths and stock levels available.