4140 Alloy Steel (UNS G41400) is a moderate-to-machine material that we run regularly for export customers. It has a density of 7.85 g/cm3, a tensile strength of 1020 MPa and a typical hardness of HB 197 (annealed). Those numbers make it the right choice for connecting rods and gear blanks, and a poor choice when cost or corrosion resistance matters more than mechanical performance.
On our machines we hold +/-0.02 mm on turned and milled features and reach Ra 0.8 um where the drawing calls for it. Standard lead time for 4140 Alloy Steel parts is 3-7 working days, including material procurement, machining and any finishing operation you specify.
4140 Alloy Steel: key properties
| Property | Value |
|---|---|
| UNS / designation | G41400 |
| Density | 7.85 g/cm3 |
| Tensile strength | 1020 MPa |
| Hardness | HB 197 (annealed) |
| Machinability | Moderate |
| Suggested cutting speed (carbide) | 120-180 m/min |
| Relative material cost | 2 of 5 |
Machining 4140 Alloy Steel: what to plan for
- Pre-hard grades need slower speeds
- Distortion on Q&T parts
- Needs stress relief
Cutting speed for 4140 Alloy Steel with carbide tooling sits around 120-180 m/min. Going faster burns the edge; going much slower causes rubbing and a poor surface. Air blast or flood coolant both work, but chip evacuation must be positive. If your part has thin walls or a lot of stock to remove, say so in the RFQ — we plan roughing, stress relief and finishing as separate operations when the geometry demands it.
Parts we machine in 4140 Alloy Steel
- Connecting rods
- Gear blanks
- Mould bases
- Heavy shafts
Most 4140 Alloy Steel work arrives as 2D drawings with a mix of critical and non-critical features. Loosening tolerance on the non-critical ones is the fastest way to cut cost, and we will tell you which features those are before we quote.
Tolerances, finish and lead time
| Item | Capability |
|---|---|
| General tolerance | +/-0.02 mm |
| Achievable surface finish | Ra 0.8 um |
| Minimum wall thickness | 0.8 mm (aluminium) / 1.0 mm (steel and stainless) |
| Typical lead time | 3-7 working days |
| Prototype quantity | 1 piece |
| Production quantity | 10 to 50,000 pieces |
Frequently asked questions
What is the lead time for 4140 Alloy Steel parts?
Standard is 3-7 working days from drawing release, assuming the material is in stock. Exotic grades and cast forms can add 5 to 10 days. Finishing such as anodizing or plating adds 3 to 5 days.
What tolerance can you hold in 4140 Alloy Steel?
+/-0.02 mm is routine on turned and milled features. Tighter than that is possible on specific features by grinding or lapping, but it is quoted separately because it changes the process.
Do you keep 4140 Alloy Steel in stock?
We hold common sizes of 4140 Alloy Steel and buy mill-certified stock for everything else. Material certificates are supplied with the parts on request.
Can you supply 4140 Alloy Steel parts with a certificate of conformity?
Yes. We issue a dimensional report, a material certificate and a certificate of conformity as standard for production orders, and full PPAP or AS9102 paperwork when the programme requires it.
Related pages
- Materials — the full index for this section.
- A2 Tool Steel CNC Machining for Blanking Dies
- M2 High-Speed Steel CNC Machining
- 1045 Carbon Steel CNC Machining: Shafts and Gears
- Hastelloy C-276 CNC Machining: Chloride Service
- Instant CNC quote
- Tolerance quick reference
- Frequently asked questions
Get a price for your part
Send a STEP file and a drawing with tolerances, material and quantity. We quote within one working day and machine in our own facility in Shenzhen — milling, turning, EDM, grinding and finishing under one roof, no trading middleman.
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