Free-Cutting Steels / LEADED
Leaded Free-Cutting Steels
Lead-alloyed free-cutting steels offer excellent chip breaking characteristics and high-speed machinability. Ideal for high-efficiency mass production on CNC automatic lathes.
Technical Specifications
Key Features
- Excellent machinability (high-speed cutting)
- Clean and short chip formation
- Reduced tool wear
- Superior surface finish after machining
- Suitable for high-volume mass production
- Available in round, hexagon, and square profiles
- Tight tolerance (h9) production capability
- Compatible with automatic lathes and CNC machines
Applications
- CNC machined precision parts
- Bolts, nuts, and studs
- Pins, bushings, and dowels
- Precision shafts and axles
- Automotive fasteners and components
- Hydraulic fittings and connectors
- Valve bodies and components
- Mass production turned parts
Dimension Table
| Form | Size Range (mm) | Tolerance | Standard Length |
|---|---|---|---|
| Round | 2 - 120 mm | h9, h10, h11 | 3 m (min 2.5 m, max 6 m) |
| Hexagon | 5 - 80 mm | h9, h10, h11 | 3 m (min 2.5 m, max 6 m) |
| Square | 5 - 70 mm | h9, h10, h11 | 3 m (min 2.5 m, max 6 m) |
Technical Notes
- 0111SMnPb30 (1.0718) is the most commonly used leaded free-cutting steel grade.
- 02Lead additive acts as a chip breaker, increasing cutting speed.
- 03EN ISO 683-4 defines hot-rolled production requirements.
- 04EN 10277 specifies cold-drawn mechanical properties.
- 05h9 tolerance is for precision applications; h11 for general-purpose use.
- 06Standard length is 3 meters; custom lengths (2.5-6m) available on request.
- 07Due to lead content, lead-free alternatives should be preferred for RoHS-compliant applications.
Other Types
What is free-cutting steel?
Free-cutting (free-machining) steel has deliberately raised sulphur (0.10–0.35% S) for high-speed machining. MnS inclusions break the chip, extending tool life and improving surface finish. The most common grades are 11SMn30 (lead-free) and 11SMnPb30 (leaded, EN 10087). It is the standard choice for bushings, pins, nipples and fittings mass-produced on automatic and CNC lathes.
Leaded vs lead-free and the trade-offs
Lead (0.15–0.35% Pb) acts as a lubricant in the cutting zone, further improving finish and tool life (11SMnPb30); however, health and environmental regulations are pushing lead-free alternatives (11SMn30 and bismuth/tellurium-treated specials). The trade-off of free-cutting steel: high sulphur reduces weldability and transverse toughness — so it is not used for welded or safety-critical parts. Where quench and tempering is needed, medium-carbon free-cutting grades such as 35S20 / 36SMn14 are selected. Delivery condition: free-cutting steel is almost always supplied as a cold drawn profile (round, square or flat, h9–h11 to EN 10277). This is not a commercial detail but a working requirement — on a bar-fed automatic lathe, sectional consistency and surface finish govern the stability of the setup and the tool life; a hot-rolled bar with scale and wide tolerances would let dimensions drift from part to part. The grade decides machinability, the drawing process decides consistency: the two choices are made together.
Frequently Asked Questions
What is the difference between 11SMn30 and 11SMnPb30?+
Both are high-sulphur free-cutting steels; 11SMnPb30 additionally contains 0.15–0.35% lead for better finish and tool life, but lead-free 11SMn30 is increasingly preferred due to RoHS/environmental limits.
Can free-cutting steel be welded?+
Not recommended. High sulphur causes hot cracking; use standard carbon steels for welded parts.
Where is free-cutting steel used?+
Bushings, shafts, nipples, unions and threaded fittings mass-produced on automatic/CNC lathes — high-volume machined parts.
Can free-cutting steel be hardened?+
Low-carbon grades (11SMn30) can only be case-hardened; if through-hardening is needed, choose medium-carbon grades like 35S20/36SMn14.
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