12L14 Free-Machining vs 1215 Free-Machining Steel
12L14 and 1215 are both free-machining resulfurized carbon steels built for high-speed screw-machine production. 1215 is resulfurized and rephosphorized; 12L14 adds lead (the 'L') to that chemistry, pushing machinability even higher. Both share ~540 MPa tensile / 415 MPa yield. 12L14 rates the best machinability of any steel (5.0), while 1215 is close behind (4.5) and lead-free. Peak machinability versus lead-free machining.
The verdict
Choose 12L14 for the absolute highest machining speed, finest finish, and longest tool life in high-volume screw-machine parts. Choose 1215 when you need excellent free-machining performance without lead — for environmental, plating, or food-contact reasons — accepting marginally lower machinability.
Side-by-side data
| Property | 12L14 Free-Machining | 1215 Free-Machining Steel |
|---|---|---|
| Category | Steel | Steel |
| Density (g/cm³) | 7.87 | 7.85 |
| Tensile strength (MPa) | 540 | 540 |
| Yield strength (MPa) | 415 | 415 |
| Elongation (%) | 10 | 10 |
| Hardness | 163 HB | 167 HB |
| Max service temp (°C) | 380 | 400 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 50 | 50 |
| Typically used for | High-volume screw-machine parts | High-volume screw-machine parts |
Which should you choose?
Choose 12L14 Free-Machining when…
- Maximum machining speed and throughput are the goal (machinability 5.0)
- Producing high-volume turned parts on screw machines
- Finest surface finish and longest tool life are required
- Lead content is acceptable for the application and market
- Fittings, fasteners, and connectors where strength demands are low
- Minimizing cycle time and cost per part dominates the decision
Choose 1215 Free-Machining Steel when…
- Lead-free material is required for RoHS, food-contact, or plating
- You still need top-tier free-machining performance (4.5 index)
- High-volume screw-machine parts with environmental restrictions
- Parts will be electroplated and lead could cause issues
- Regulatory or customer specs prohibit leaded steels
- Excellent machinability matters but not at the cost of lead
Key differences that matter
- Both are free-machining carbon steels with the same listed strength (~540 MPa tensile / 415 MPa yield)
- 12L14 is leaded (resulfurized, rephosphorized + lead); 1215 is resulfurized/rephosphorized but lead-free
- Machinability: 12L14 rates 5.0 (best of any steel) vs 1215 at 4.5 — the lead gives 12L14 the edge
- Lead and sulfur form free-machining inclusions that break chips and reduce cutting forces in both
- Neither is meant for structural strength or welding — sulfur and lead make them prone to weld cracking
- Corrosion resistance is poor (1.5/5) for both; plating or coating is needed in service
- Cost is similar (~1.2 index each); the choice usually hinges on whether lead is permitted
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Open the Material SelectorGet a Quote →Frequently asked questions
What is the difference between 12L14 and 1215 steel?
Both are free-machining resulfurized, rephosphorized carbon steels, but 12L14 adds lead (the 'L') to boost machinability further. 12L14 rates the highest machinability of any steel (5.0) versus 1215's 4.5. They share similar strength (~540 MPa tensile). The main reason to pick 1215 is when lead-free material is required.
Is 12L14 better than 1215 for machining?
12L14 machines slightly better thanks to its lead content, rating 5.0 versus 1215's 4.5 — meaning higher speeds, finer finishes, and longer tool life. The difference is real but modest. If lead is permitted and you want absolute peak throughput, choose 12L14; if you need lead-free, 1215 still machines excellently.
Can 12L14 and 1215 steel be welded?
Neither is recommended for welding. The high sulfur (and lead in 12L14) that makes them so machinable also makes welds brittle and crack-prone. These steels are designed for high-speed machined parts, not weldments. If a part must be welded, choose a low-carbon steel like 1018 instead of a free-machining grade.
Why choose lead-free 1215 over 12L14?
Choose 1215 when lead is prohibited — for RoHS compliance, food or drinking-water contact, certain plating processes, or customer specifications that ban leaded steel. 1215 delivers nearly the same free-machining performance (4.5 vs 5.0) without the lead, making it the go-to free-machining grade where environmental or regulatory limits apply.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.