CNC Polishing Invar is a core capability at VT machining. We combine controlled finishing with material-aware setup for Invar — an alloy that is ultra-low thermal expansion — to produce parts that meet your specification first time.
CNC Polishing Capability for Invar
- Mirror finish capable
- Ra to 0.05 µm
- Cosmetic & sealing faces
- Multi-stage abrasives
Invar Material Data
| Density | 8.11 g/cm³ |
|---|---|
| Tensile strength | 450–590 MPa |
| Yield strength (0.2%) | 275 MPa |
| Hardness | 130–160 HB |
| Melting point | 1427 °C |
| Thermal conductivity | 10.5 W/m·K |
| Thermal expansion | 1.2 (0–100 °C) ×10⁻⁶/K |
| Electrical conductivity | 2% |
| Machinability (C36000 = 100%) | 25% |
| Grades we run | Invar 36, Super Invar 32-5, Alloy 42, Alloy 46 |
Published typical values for Invar 36 (FeNi36). Other grades in the family differ — the certificate supplied with your order carries the actual heat-lot figures.
The low expansion is the whole point, so machining stress is the enemy. Rough, stress-relieve at 315–425 °C, then finish — otherwise the part moves after it leaves the machine.
How CNC Polishing Invar Works
Abrasive media or tooling refine the Invar surface in controlled stages, removing the previous step's marks until the target roughness and edge condition are reached.
Every job begins from your CAD model or 2D drawing. Fixturing and tool paths are planned so the most critical dimensions are produced in the most rigid, repeatable setup. Critical dimensions are checked on the first part and monitored through the run.
Achievable Tolerances for CNC Polishing Invar
| 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 Invar
Invar offers a useful combination of properties: it is ultra-low thermal expansion. Those characteristics shape how we approach finishing — from tool and parameter selection to work-holding and coolant.
If your application is sensitive to alloy condition, we agree the specification in writing and document it. Stock is sourced from reputable suppliers so what you order is what you receive.
CNC Polishing Tolerances & Surface Finish
Finishing brings Invar to a defined roughness target — from a uniform satin to Ra values as low as 0.05 µm — with controlled, repeatable edge breaks.
Final tolerances are governed by the material's behaviour, wall thickness and overall stiffness. We give honest DFM feedback if a callout would be costly or better achieved another way.
Design Tips for CNC Polishing Invar
A few design choices make a real difference to cost and quality. Telling us the target Ra, the cosmetic faces and any masking needs lets us finish Invar 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
Consistent quality comes from disciplined process control. Critical dimensions on Invar 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 Invar 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 Polishing Invar
CNC Polishing of Invar 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 Polishing Invar
Ordering Invar 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.
Parts We Have Run in Invar
Three representative CNC Polishing Invar 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.
Cosmetic housing
- Material
- Invar
- Size
- 150 × 90 mm visible face
- Key callouts
- Uniform satin, no directional lines
- Batch
- 2,500 pcs
Grained in one direction with datum faces masked so they keep their tolerance.
Deburred stamping
- Material
- Invar
- Size
- 40 × 25 × 1 mm
- Key callouts
- Edge break 0.05–0.15 mm, no sharp edges
- Batch
- 30,000 pcs
Vibratory finished in media sized to reach every internal cutout.
Passivated stainless fitting
- Material
- Invar
- 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.
Finishing Options for Invar
| Finish | Thickness / effect | Why it gets specified |
|---|---|---|
| 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 Invar
- 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 Invar 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 Invar
Send the drawing, the Invar 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 Invar and how is it done?
CNC Polishing Invar refers to cNC polishing refines surfaces to a smooth, reflective finish for cosmetic and functional needs. Applied to Invar — ultra-low thermal expansion — VT machining produces each part to your CAD drawing, selecting parameters from your tolerance, finish and quantity requirements.
Which industries use CNC Polishing Invar parts?
CNC Polishing Invar parts are used across aerospace, medical, automotive, electronics, semiconductor and general industrial sectors — anywhere precise Invar components are required.
Why is Invar a good choice for CNC Polishing?
Invar is ultra-low thermal expansion, which makes it well suited to CNC Polishing. We tune the process to the alloy so the finished Invar finishing part meets your dimensional and functional requirements.
Does CNC Polishing Invar require dedicated tooling?
Most Invar finishing work uses standard cutting tools and CNC programs; dedicated fixtures are made only when geometry or volume requires them.
What surface finish is achievable on Invar with CNC Polishing?
Our finishing processes refine Invar surfaces to Ra values as low as 0.05 µm for cosmetic or sealing faces.
How clean are the edges produced by CNC Polishing on Invar?
Our deburring leaves Invar with a consistent, controlled edge break and burr-free surfaces.