CNC Milling 309S Stainless Steel is part of VT machining's grade-specific capability. 309S Stainless Steel is corrosion resistant, strong and hygienic, and we combine controlled machining with material-aware setup to produce parts that meet your specification.
CNC Milling Capability for 309S Stainless Steel
- Austenitic/martensitic grades
- Corrosion resistant
- Tolerance to ±0.01 mm
- Typical hardness 70–200 HB (annealed)
309S Stainless Steel Material Data
| Density | 8.00 g/cm³ |
|---|---|
| Tensile strength | 515 MPa |
| Yield strength (0.2%) | 205 MPa |
| Hardness | 170 HB |
| Melting point | 1400–1450 °C |
| Thermal conductivity | 16.2 W/m·K |
| Thermal expansion | 17.3 ×10⁻⁶/K |
| Electrical conductivity | 2.4% |
| Machinability (C36000 = 100%) | 45% |
| Grades we run | 303, 304/304L, 316/316L, 321, 410, 416, 420, 17-4PH, 2205 duplex |
Published typical values for 304. Other grades in the family differ — the certificate supplied with your order carries the actual heat-lot figures.
It work-hardens the moment a tool dwells. Constant feed and positive-rake tooling; a rubbing pass leaves a glazed skin the next tool cannot get through.
Machining 309S Stainless Steel with CNC Milling
The machinability of 309S Stainless Steel is moderate; work-hardens, so positive-rake tooling and steady feeds are used to avoid glazing. For CNC Milling we select tooling, feeds, speeds and coolant to match, keeping the 309S Stainless Steel workpiece stable and the result accurate.
Because we machine 309S Stainless Steel regularly, proven settings shorten setup and keep quality repeatable across reorders.
Achievable Tolerances for CNC Milling 309S Stainless Steel
| Feature | Standard | Precision |
|---|---|---|
| Linear dimension (< 100 mm) | ±0.05 mm | ±0.010 mm |
| Linear dimension (100–300 mm) | ±0.10 mm | ±0.025 mm |
| Hole diameter (reamed) | H9 | H7 |
| True position of hole pattern | ±0.10 mm | ±0.025 mm |
| Flatness over 100 mm | 0.05 mm | 0.015 mm |
| Perpendicularity | 0.10 mm | 0.020 mm |
| Surface finish, as machined | Ra 1.6 µm | Ra 0.4 µm |
Standard is what a normal quotation assumes. Precision is available on nominated features and is priced separately, because it needs extra setups, in-process gauging and CMM verification. Call out only the features that need it — blanket-tightening a drawing is the single most common reason a quote comes back expensive.
Why 309S Stainless Steel?
Specifying 309S Stainless Steel for CNC Milling 309S Stainless Steel is usually about its properties: corrosion resistant, strong and hygienic. Tell us the condition you need and we machine to it.
CNC Milling Tolerances & Surface Finish
For CNC Milling, dimensional and positional tolerances around ±0.01 mm are routine, tightening toward ±0.005 mm on precision setups. Surface finish on machined faces typically falls in the Ra 0.4–1.6 µm range depending on tooling and pass strategy.
The tightest tolerances are reserved for the features your drawing flags as critical. Share your tolerance scheme and we will confirm what is realistic before quoting.
Design Tips for CNC Milling 309S Stainless Steel
A few design choices make a real difference to cost and quality. Generous internal radii, sensible pocket depth-to-width ratios and avoiding very thin unsupported walls all reduce cost and improve accuracy in 309S Stainless Steel. If you send your model early, we will return practical DFM feedback before you commit to production.
CNC Milling Quality & Inspection
Consistent quality comes from disciplined process control. Critical dimensions on 309S Stainless Steel parts are checked in-process and verified at final inspection using calibrated instruments and, where required, CMM measurement. Full documentation — dimensional reports, mill certs, FAIR — is available when your programme needs it.
Secondary Operations & Finishing
We complete 309S Stainless Steel components with the secondary steps your drawing calls for. We arrange heat treatment, surface treatment, marking and assembly as needed. Tell us the final spec and we will plan the full route so parts arrive ready to use.
Applications of CNC Milling 309S Stainless Steel
CNC Milling of 309S Stainless Steel supports parts across aerospace, medical, automotive, electronics, semiconductor, energy and general industrial sectors. We scale from one-off prototypes to ongoing production while holding the same quality.
How to Order CNC Milling 309S Stainless Steel
Ordering 309S Stainless Steel parts is straightforward. Provide the drawing, material, quantity and any certification needs. Our engineers reply — in English — with feasibility, pricing and a realistic lead time, usually within one business day.
Finishing Options for 309S Stainless Steel
| Finish | Thickness / effect | Why it gets specified |
|---|---|---|
| Citric passivation | — | ASTM A967 / AMS 2700, removes free iron |
| Electropolish | 5–25 µm removed | Ra improves by roughly half, hygienic surface |
| Brushed / grained | Ra 0.4–1.6 µm | No. 4 finish, directional |
| PVD coating | 2–5 µm | TiN, TiCN for wear surfaces |
| Deburr / edge break | 0.05–0.3 mm | All parts unless the drawing says otherwise |
| Bead blast | Ra 1.6–3.2 µm | Uniform matt finish, hides tool marks |
| Laser marking | — | Part number, lot code, data matrix |
No drawing yet? Build one in the browser.
Set the metal, dimensions and features, watch the 3D model update as you type, then switch to the 2D sheet to add dimensions and tolerances. Download it or send it straight to us with your RFQ.
What We Need to Quote CNC Milling 309S Stainless Steel
- GeometrySTEP or IGES for the 3D model, plus a PDF drawing if you have tolerance callouts. A dimensioned sketch is enough to start.
- MaterialThe exact 309S Stainless Steel grade and condition — temper, heat-treat state or hardness. If you are not sure, tell us the function and we will suggest one.
- QuantityPrototype count and the expected annual volume. Both change how the part is made and therefore what it costs.
- TolerancesWhich features are critical. Everything else runs to our standard tolerance, which is what keeps the price sensible.
- FinishSurface treatment, cosmetic requirements, and any faces that must be masked.
- DocumentsWhether you need a material certificate, dimensional report, FAIR or PPAP with the shipment.
Missing something from the list is not a problem — send what you have. We will come back with the specific questions rather than a generic form.
309S Stainless Steel in Other Processes
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Send the drawing, the 309S Stainless Steel condition and the quantity — pricing and lead time come back the same or next business day.
Request a QuoteFrequently Asked Questions
Why is 309S Stainless Steel a good choice for CNC Milling?
309S Stainless Steel is corrosion resistant, strong and hygienic, which makes it well suited to CNC Milling. We tune the process to the alloy so the finished 309S Stainless Steel machining part meets your dimensional and functional requirements.
How clean are the edges produced by CNC Milling on 309S Stainless Steel?
Machined 309S Stainless Steel edges are clean and to specification; edge-break or deburring is added when your drawing calls for it.
What tolerances can you hold for CNC Milling 309S Stainless Steel?
Achievable tolerances for 309S Stainless Steel machining depend on the alloy, geometry and feature size. Milling holds positional and dimensional tolerances to around ±0.01 mm, tighter with precision setups. Exact figures are confirmed against your drawing callouts.
What material thickness or size range suits CNC Milling 309S Stainless Steel?
We machine 309S Stainless Steel across a broad size range; share your part envelope for confirmation.
What surface finish is achievable on 309S Stainless Steel with CNC Milling?
Surface finish on 309S Stainless Steel is controlled to your specification; we confirm the achievable Ra against your callout.
Which industries use CNC Milling 309S Stainless Steel parts?
CNC Milling 309S Stainless Steel parts are used across aerospace, medical, automotive, electronics, semiconductor and general industrial sectors — anywhere precise 309S Stainless Steel components are required.