12L14 Leaded Free-Machining Steel (UNS G12144)
The fastest-machining steel there is: lead, sulfur and phosphorus give short chips and a bright finish at high speed — for high-volume screw-machine fittings, pins and adapters in light duty.
What 12L14 is.
12L14 is a low-carbon steel with lead, sulfur and phosphorus added purely for machinability. The lead acts as an internal lubricant and the sulfides break chips, so the alloy turns at the highest speeds of any carbon steel with an excellent surface finish. Strength is modest, it should not be welded, and toughness is poor, so it belongs in lightly loaded fittings and pins made in quantity. Not for pressure-boundary, structural, fatigue-loaded or low-temperature bolting.
We run 12L14 on the Swiss lathes for fittings, adapters, pins and small components, and plate or black oxide them for appearance and storage protection.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.15 |
| Manganese | Mn | 0.85 | 1.15 |
| Phosphorus | P | 0.04 | 0.09 |
| Sulfur | S | 0.26 | 0.35 |
| Lead | Pb | 0.15 | 0.35 |
Per SAE J403 / ASTM A29, confirmed by Alro, AZoM and Eaton Steel Bar.
Mechanical properties.
| Condition (¾–1¼ in. round) | Tensile strength, typical (ksi) | Yield strength 0.2% offset, typical (ksi) | Elongation, typical (%) | Reduction of area, typical (%) | Hardness, typical |
|---|---|---|---|---|---|
| Cold drawn | 78 | 60 | 10 | 35 | 163 HB |
Typical values for cold-drawn bar, confirmed by AZoM and Alro (1-in. average). For reference, Saarstahl’s cold-drawn minimums for 16 to 40 mm are 68 ksi tensile and 54 ksi yield. ASTM A108 sets no mechanical requirements.
Specifications that apply.
How 12L14 ships from Houston.
- Machined components from certified bar
- Fittings, adapters and bushings
- Pins and spacers for light duty
12L14 fasteners we make.
Every item is manufactured to your drawing or standard in 12L14, imperial or metric, with an EN 10204 3.1 certificate.
What is 12L14 steel?
12L14 exists to be machined. Lead does not dissolve in steel; it sits as microscopic particles that smear over the tool and shear easily, so cutting forces and tool wear fall and surface finish improves. Sulfur and phosphorus add chip breaking. The trade is toughness and weldability, which are poor, and modest strength, and lead's environmental restrictions mean some customers now specify the unleaded 1215 or 1117 instead.
Testing, certification and marking
- Hardness tested per lot; tensile on request or where the specification requires it
- Manufacturer's identification and heat number on every piece where size allows
- EN 10204 3.1 material test report with heat number and chemistry
- PMI verification on request
1117 Free-Machining Carbon Steel (UNS G11170)
Low-carbon steel with added sulfur and manganese for fast machining and a good carburized case — the screw-machine grade for case-hardened pins, gears and fittings.
ASTM A108 / A29 / A311 bar1144 Free-Machining Carbon Steel (UNS G11440)
Medium-carbon free-machining steel that is strong straight from the bar: about 108 ksi cold drawn, machines well, hardens by induction — the Stressproof® family grade for shafts and studs without heat treatment.
ASTM A582 bar · ASTM F593 bolts303 Free-Machining Stainless Steel (UNS S30300)
304 with sulfur added for fast, clean machining — the grade for complex turned fasteners and fittings where corrosion resistance can give a little.