ISO 4762 Hex Socket Head Cap Screw | DIN 912 Allen Bolt 8.8–12.9 Supplier
Product Introduction
The hex socket head cap screw is the quiet workhorse of every machine shop on earth. The head is a plain cylinder with a hex socket sunk into it, so you can drive it from straight above. No protruding hex head, no washer needed, no corner to catch on a cover plate. That's why mold builders and automation engineers reach for it: it sinks flush into a counterbore and still takes serious load.
ISO 4762 is the standard that governs it today. DIN 912 was the old number, and honestly, half of South America still orders it by that name. Same head, same socket, same thread — the ISO edition just tightened the tolerance grades. We print both designations on the box so your warehouse guys never have to guess.
What you actually get from us: quenched and tempered steel in 8.8, 10.9, and 12.9, or austenitic stainless in A2 and A4. The 12.9 class runs 1200 MPa nominal tensile, proof stress 1080 MPa — the strongest class normally made in a socket screw. It's also the class people fake the most, which is why our 12.9 batches ship with a tensile test report, not just a heat number on paper.
A few things we do differently at the plant. We test-drive every heat of 12.9 for hydrogen embrittlement risk before plating — that's the failure nobody sees coming, and it costs machines. We keep M4–M12 in stock across the common lengths, so mixed orders move fast. And we pack for the sea route to Santos, Callao, Valparaíso or Buenos Aires with VCI protection, because a container deck gets hot and humid, and rusted screws are the fastest way to lose a customer.
Full Specification
| Property | 8.8 | 10.9 | 12.9 |
|---|---|---|---|
| Nominal tensile strength Rm (MPa) | 800 | 1000 | 1200 |
| Minimum tensile strength Rm,min (MPa) | 800 (d ≤ 16) / 830 (d > 16) | 1040 | 1220 |
| Nominal proof stress Rp0.2 (MPa) | 640 | 900 | 1080 |
| Minimum proof stress Rp0.2,min (MPa) | 640 (d ≤ 16) / 660 (d > 16) | 940 | 1080 |
| Guarantee (proof) stress Sp (MPa) | 580 (d ≤ 16) / 600 (d > 16) | 830 | 970 |
| Hardness — Vickers HV (F ≥ 98 N) | 250 – 320 | 320 – 380 | 385 – 435 |
| Hardness — Brinell HB | 238 – 304 | 304 – 361 | 366 – 414 |
| Hardness — Rockwell HRC | 22 – 32 | 32 – 39 | 39 – 44 |
| Impact energy AKV (J), min | 30 | 20 | 15 |
| Recommended material | Low-carbon alloy steel (boron, Mn or Cr) or medium-carbon steel, quenched & tempered | Medium-carbon steel / low- or medium-carbon alloy steel, quenched & tempered | Alloy steel, quenched & tempered |
| Minimum tempering temperature (°C) | 425 | 340 (alloy) / 425 | 380 |
| Finish | Typical service | Remarks |
|---|---|---|
| Plain (as manufactured) | Dry / internal assemblies | No coating; oiled on request |
| Black oxide (oxidation) | Mild indoor environment, aesthetic assemblies | Minimal dimensional build-up |
| Electro zinc plated, passivated | General corrosion protection | Typical plating 5 – 12 µm; hydrogen-relief baking required for classes ≥ 10.9 |
| Zinc-nickel (ZnNi) | Automotive / high-corrosion duty | e.g. ZnNi 5/Cn/T2 per ISO 4042 notation |
| Zinc flake (Dacromet-type) | High corrosion, spring-steel or hardened parts | Non-electrolytic; no hydrogen embrittlement risk |
| Hot-dip galvanized | Outdoor / structural applications (larger sizes) | Thick coating; thread dimensions to be considered |
| PTFE / lubricant coated | Friction-sensitive or chemical duty | Reduces tightening torque scatter |
|
ASTM A967 / A380 |
Chemical passivation of stainless steel — surface process |
Size Chart
| Thread size d (6g) |
Pitch P |
Head dia. dk (max) |
Head height k |
Socket across flats s |
Nominal length l (range) |
|---|---|---|---|---|---|
| M1.6 | 0.35 | 3.0 | 1.6 | 1.5 | 2.5 – 16 |
| M2 | 0.4 | 3.8 | 2.0 | 1.5 | 3 – 20 |
| M2.5 | 0.45 | 4.5 | 2.5 | 2.0 | 4 – 25 |
| M3 | 0.5 | 5.5 | 3.0 | 2.5 | 5 – 30 |
| M4 | 0.7 | 7.0 | 4.0 | 3.0 | 6 – 40 |
| M5 | 0.8 | 8.5 | 5.0 | 4.0 | 8 – 50 |
| M6 | 1.0 | 10.0 | 6.0 | 5.0 | 10 – 60 |
| M8 | 1.25 | 13.0 | 8.0 | 6.0 | 12 – 80 |
| M10 | 1.5 | 16.0 | 10.0 | 8.0 | 16 – 100 |
| M12 | 1.75 | 18.0 | 12.0 | 10.0 | 20 – 120 |
| M14 | 2.0 | 21.0 | 14.0 | 12.0 | 25 – 140 |
| M16 | 2.0 | 24.0 | 16.0 | 14.0 | 25 – 160 |
| M20 | 2.5 | 30.0 | 20.0 | 17.0 | 30 – 200 |
| M24 | 3.0 | 36.0 | 24.0 | 19.0 | 40 – 200 |
| M30 | 3.5 | 45.0 | 30.0 | 22.0 | 45 – 200 |
| M36 | 4.0 | 54.0 | 36.0 | 27.0 | 55 – 200 |
Notes: (1) Values per GB/T 70.1-2008 dimension table (identical to ISO 4762:2004). (2) For M16 – M36, earlier standard editions permitted a smaller alternative socket size (e.g. s = 12 for M16); current production follows the primary values above. (3) M42 – M64 and fine-pitch variants quoted against the current ISO 4762:2004 document before production. (4) Stress area As for proof-load checks: M6 = 20.1 mm², M8 = 36.6 mm², M10 = 58.0 mm², M12 = 84.3 mm², M16 = 157 mm², M20 = 245 mm², M24 = 353 mm², M30 = 561 mm².
Applications
- Machine tools and accessories — head clamping, slideway and fixture mounting where a flush head keeps the work envelope clean
- Automation equipment — robot end-effectors, conveyor frames, sensor and rail brackets
- Molds and dies — mold plate clamping, ejector systems, hot-runner assemblies (12.9 is the standard pick here)
- Vehicles and heavy machinery — engine and transmission housings, mining and agricultural equipment common across Chile, Peru and Brazil
- Hydraulic systems — manifold and valve mounting on pumps and cylinders
- Marine and food processing (A4) — port equipment, fishing vessels, dairy and beverage lines where washdown and salt air kill plain steel
Why Fasto
We're the plant, not a middleman
20+ years exporting screws, bolts, nuts, rivets and nails. Own factory, own heat-treatment line, own plating line. When you ask about a heat treatment curve or a plating thickness, the answer comes from the shop floor, not from a re-seller guessing.
Certificates that survive an audit
Company level: IATF 16949, ISO 9001. Product level: CE, SGS, RoHS. Batch level: mill certificate, tensile and hardness test report on request. Your QA team won't have to chase documents after the container lands.
Stock where it matters
M4 – M12 in 8.8 / 10.9 / 12.9 and A2-70 across the common lengths sit on the shelf. Mixed-carton orders ship in about a week. That covers 80% of the urgent calls we get from distributors.
Packed for the route, not the shelf
VCI paper, rust-preventive oil, seaworthy cartons, shrink-wrapped pallets. We've shipped to Santos, Callao, Valparaíso, Cartagena and Buenos Aires enough times to know what a container deck does to plain steel in the tropics.
Pain Points & Solutions
*Screws arrive rusted after sea freight
Long transit through the tropics, container condensation, plain packing. We've pulled rusted screws out of competitors' boxes at ports — not something we enjoy doing.Our fix: rust-preventive oil + VCI paper as standard, VCI bags and desiccant for long routes, zinc flake (Dacromet-type) or hot-dip galvanized when the job really lives outdoors.
*Fake 12.9 — the silent breaker
12.9 is the class most commonly faked: lower-grade steel, skipped heat treatment, wrong hardness. It looks right until a mold or a machine frame lets go mid-shift.
Our fix: every 12.9 batch ships with a tensile test report and hardness reading. Material certificate ties the heat number back to the melt. Ask for the baking record on plated 10.9/12.9 — we keep it.
*Socket strips and rounds out under torque
Driving a socket screw past its torque spec, or with a worn hex key, rounds the socket and jams the job. Common with impact drivers on 12.9 parts.
Our fix: controlled socket hardness and clean geometry in the broaching step; we supply a tightening torque table per size and class, and we say it plainly — don't use impact drivers on socket screws.
*Can't buy small lots, can't get the odd size
Distributors in Latin America often need a carton, not a container. Suppliers quoting MOQ 50,000 pieces make that impossible.
Our fix: MOQ from one carton on standard sizes (M3 – M16). Mixed cartons across sizes and lengths count as one line.
*Non-standard lengths and M42 – M64 quoted per project.
Customs paperwork chaos at the port
Missing material certificates, wrong origin documents, invoice descriptions that don't match the packing list — customs holds the container, the buyer pays the demurrage.
Our fix: commercial invoice, packing list, certificate of origin and material certificates prepared together, cross-checked before the ship sails. IATF 16949 and ISO 9001 copies on request.
*Lead times that kill production plans
Special orders that take 60–90 days force shops to pad inventory or stop lines. Nobody budgets for that.
Our fix: stocked M4 – M12 ships in ~1 week; standard production 25–35 days; we give a real shipping date in the quotation and hold it.
FAQSí — DIN 912 fue sustituida por ISO 4762:2004. Mismas dimensiones de cabeza, hexágono y rosca. Por eso marcamos ambas designaciones en cada caja: nadie en el almacén tiene que adivinar.
Para M8 classe 12.9, o torque de aperto fica em torno de 32–39 N·m com fator de atrito µ = 0.14 (apertado a seco, use os valores mais baixos). Enviamos a tabela completa de torque por tamanho e classe junto com o pedido.
Para costa y ambiente húmedo, 316 (A4). El molibdeno del A4 resiste la corrosión por picaduras mucho mejor que el A2 (304). Plantas pesqueras y portuarias de Chile, Perú y Brasil lo aprenden por las malas con tornillos A2 manchados.
Marítimo a Valparaíso o Callao: 25–35 días desde embarque. A Santos: 30–40 días. Con stock, el embarque sale en ~1 semana después de tu confirmación. Aéreo disponible para urgencias, aunque el flete pesa en el precio.
Yes. DIN 912 was superseded by ISO 4762:2004. The two call out the same head, socket and thread dimensions, and the old DIN number is still used across South American catalogs. We mark every box with both designations so nobody gets confused at the warehouse.
12.9 is the top strength class normally made in socket head cap screws. Nominal tensile strength is 1200 MPa, proof stress 1080 MPa. The screw is quenched and tempered, hardness 385–435 HV. It's the class for high-load machine and mold clamping jobs — and the class most likely to be faked, which is why our 12.9 orders ship with a batch tensile report.
Q9. Which stainless should I pick for a coastal plant, A2 or A4?
For humid or salt-air service, go A4. A4-70 is 316-type austenitic with molybdenum, so it resists pitting far better than A2 (304-type). Buyers in Chile, Peru and coastal Brazil have learned this the hard way with rust-stained A2 screws on fishing and port equipment. A4-80 is the cold-worked higher-strength option when you need more load on top of that corrosion resistance.
For standard sizes M3–M16 in 8.8, 10.9, 12.9 and A2-70, MOQ is one carton — often 2,000 to 5,000 pieces depending on size. Bigger or non-standard sizes go to 5,000–10,000 pieces. We keep M4–M12 in stock, so a mixed carton order can ship within a week.
Around 32–39 N·m at a friction factor of µ = 0.14, dry threads. Use the lower end of the range for plated or lubricated threads. We include a full torque table per size and property class with every order — and we recommend a torque wrench, not an impact driver, on socket head screws.
Yes. Fine-pitch variants per ISO 261/262 and non-standard lengths are available on request, subject to minimum order quantities. M42–M64 dimensions are confirmed against the current ISO 4762:2004 document before we quote — we don't guess on big diameters.