CNC Polishing Alloy Steel is a core capability at VT machining. We combine controlled finishing with material-aware setup for Alloy Steel — an alloy that is high strength and hardenability for demanding parts — to produce parts that meet your specification first time.
CNC Polishing Capability for Alloy Steel
- Mirror finish capable
- Ra to 0.05 µm
- Cosmetic & sealing faces
- Multi-stage abrasives
Alloy Steel Material Data
| Density | 7.85 g/cm³ |
|---|---|
| Tensile strength | 655–1020 MPa |
| Yield strength (0.2%) | 415–900 MPa |
| Hardness | 197–302 HB |
| Melting point | 1416 °C |
| Thermal conductivity | 42.6 W/m·K |
| Thermal expansion | 12.3 ×10⁻⁶/K |
| Electrical conductivity | 8% |
| Machinability (C36000 = 100%) | 65% (annealed) |
| Grades we run | 4140, 4340, 8620, 20CrMnTi, 42CrMo4, 20MnCr5 |
Published typical values for 4140 (Q&T). Other grades in the family differ — the certificate supplied with your order carries the actual heat-lot figures.
Heat treatment moves the part. Anything held tighter than ±0.02 mm is machined soft, hardened, then ground or hard-turned to final size.
How CNC Polishing Alloy Steel Works
Abrasive media or tooling refine the Alloy Steel surface in controlled stages, removing the previous step's marks until the target roughness and edge condition are reached.
We start from your supplied geometry and tolerance scheme. The setup is designed to minimise re-clamping, which protects positional accuracy across features. A first article is verified against the drawing before the balance of the batch is released.
Achievable Tolerances for CNC Polishing Alloy Steel
| Feature | Standard | Precision |
|---|---|---|
| Surface roughness | Ra 0.8 µm | Ra 0.05 µm |
| Edge break | 0.1–0.3 mm | 0.05 ±0.02 mm |
| Material removed | 0.02 mm | 0.005 mm |
| Bore roundness after honing | 0.005 mm | 0.002 mm |
| Cross-hatch angle | 45° ±10° | 45° ±5° |
| Cosmetic grade | uniform satin | mirror, no visible lines |
| Masking of datum faces | on request | standard |
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.
Working with Alloy Steel
Alloy Steel is high strength and hardenability for demanding parts. We translate those properties into a process plan: the right tooling, speeds, feeds and fixturing for the alloy.
Where the grade, temper or heat-treat condition matters to performance, we confirm it with you and can supply material certificates. Material is procured to recognised standards for consistent, repeatable results.
Secondary Operations & Finishing
Most Alloy Steel parts need some finishing, which we manage in-house or through vetted partners. Options include deburring and edge-breaking, heat treatment, surface grinding, polishing, and plating or anodising for corrosion resistance and appearance. Give us the finished-part requirement and we will sequence every operation correctly.
Design Tips for CNC Polishing Alloy Steel
Small design adjustments often cut cost and lead time. Telling us the target Ra, the cosmetic faces and any masking needs lets us finish Alloy Steel efficiently without over-processing. If you send your model early, we will return practical DFM feedback before you commit to production.
CNC Polishing Quality & Inspection
Quality is built in, not inspected on. We monitor key features during the run and confirm them at final inspection, with CMM verification available for tight tolerances. We provide the inspection and traceability records your quality system requires.
CNC Polishing Tolerances & Surface Finish
Finishing brings Alloy Steel to a defined roughness target — from a uniform satin to Ra values as low as 0.05 µm — with controlled, repeatable edge breaks.
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.
Applications of CNC Polishing Alloy Steel
Alloy Steel parts made this way are found throughout aerospace, medical, automotive, electronics and industrial equipment. Prototype, bridge and production volumes are all welcome.
How to Order CNC Polishing Alloy Steel
Starting your project takes one email. Send your CAD or 2D drawing, the Alloy Steel grade and condition, the quantity and any finish or inspection requirements. We respond quickly with price, lead time and any DFM notes, in clear English.
Parts We Have Run in Alloy Steel
Three representative CNC Polishing Alloy Steel jobs, with the callouts that actually drove the process plan. Yours will differ — these are here so you can judge whether your part is in our range before you spend time on an RFQ.
Passivated stainless fitting
- Material
- Alloy Steel
- Size
- Ø18 × 40 mm
- Key callouts
- ASTM A967 citric passivation, no free iron
- Batch
- 5,000 pcs
Passivated after all machining, then tested with a copper sulphate check.
Hydraulic bore
- Material
- Alloy Steel
- Size
- Ø32 × 200 mm
- Key callouts
- Ra 0.4 µm cross-hatch 45°, roundness 0.003 mm
- Batch
- 600 pcs
Honed in three stages; the cross-hatch is what holds the oil film.
Sealing face
- Material
- Alloy Steel
- Size
- Ø60 mm face
- Key callouts
- Ra 0.2 µm, flatness 0.005 mm
- Batch
- 1,000 pcs
Lapped after grinding; the seal spec is a roughness number, not a dimension.
Finishing Options for Alloy Steel
| Finish | Thickness / effect | Why it gets specified |
|---|---|---|
| Through hardening | — | 30–55 HRC, ground afterwards for tight sizes |
| Case hardening (carburise) | 0.3–1.2 mm case | 58–62 HRC surface, tough core |
| Nitride | 0.1–0.5 mm | 900–1100 HV, minimal distortion |
| Black oxide | 1–2 µm | Cosmetic + light corrosion protection |
| Zinc / nickel plate | 5–25 µm | Corrosion protection |
| 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 Polishing Alloy 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 Alloy 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.
Other Metals for CNC Polishing
Other Processes for Alloy Steel
Send the drawing, the Alloy Steel grade and the quantity. You get pricing, lead time and any DFM notes back — usually within one business day.
Request a QuoteFrequently Asked Questions
What is CNC Polishing Alloy Steel and how is it done?
CNC Polishing Alloy Steel refers to cNC polishing refines surfaces to a smooth, reflective finish for cosmetic and functional needs. Applied to Alloy Steel — high strength and hardenability for demanding parts — VT machining produces each part to your CAD drawing, selecting parameters from your tolerance, finish and quantity requirements.
Can VT machining make custom Alloy Steel parts to my drawing?
Yes. Alloy Steel Alloy Steel finishing is made to order from your CAD/2D drawing. Share your geometry, material grade, tolerance and quantity and we will confirm feasibility, lead time and pricing.
What is the typical lead time and minimum order for CNC Polishing Alloy Steel?
CNC Polishing prototypes for Alloy Steel can be produced quickly and scaled to series production. Send your drawing and quantity and we will advise lead time and any minimum order.
What material thickness or size range suits CNC Polishing Alloy Steel?
We machine Alloy Steel across a broad size range; share your part envelope for confirmation.