CNC Grinding Invar from VT machining delivers precision Invar parts produced to your exact drawing. CNC grinding removes material with a precision abrasive wheel to achieve tight dimensional tolerances and superior surface finish, and we tune every parameter to the behaviour of Invar, which is ultra-low thermal expansion.
CNC Grinding Capability for Invar
- Surface finish to Ra 0.1–0.4 µm
- Dimensional tolerance to ±0.002 mm
- Flatness/parallelism within 0.005 mm
- Wheel grit selected per alloy hardness
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 Grinding Invar Works
An abrasive wheel removes a fine, controlled layer from the Invar part. Wheel specification, dressing interval, infeed and coolant are matched to the alloy's hardness so the surface is not burned or left with residual stress.
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 Grinding Invar
| Feature | Standard | Precision |
|---|---|---|
| Size (OD, ID, thickness) | ±0.005 mm | ±0.002 mm |
| Flatness over 100 mm | 0.010 mm | 0.003 mm |
| Parallelism | 0.010 mm | 0.003 mm |
| Roundness | 0.005 mm | 0.002 mm |
| Squareness | 0.010 mm | 0.005 mm |
| Surface finish | Ra 0.4 µm | Ra 0.1 µm |
| Workpiece hardness | up to 62 HRC | up to 65 HRC |
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.
CNC Grinding Tolerances & Surface Finish
Ground Invar reaches single-micron tolerances on size, flatness and parallelism, with surface finishes down to Ra 0.1–0.4 µm — and a near-mirror finish on suitable alloys.
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.
Working with Invar
Invar is ultra-low thermal expansion. 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.
Design Tips for CNC Grinding Invar
Small design adjustments often cut cost and lead time. Allowing adequate grind stock, specifying realistic flatness over the true datum, and relieving corners help us hit tight tolerances on Invar efficiently. If you send your model early, we will return practical DFM feedback before you commit to production.
Secondary Operations & Finishing
Most Invar 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.
CNC Grinding 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.
Applications of CNC Grinding Invar
Invar 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 Grinding Invar
Starting your project takes one email. Send your CAD or 2D drawing, the Invar 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 Invar
Three representative CNC Grinding 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.
Ceramic-coated shaft journal
- Material
- Invar
- Size
- Ø45 × 180 mm
- Key callouts
- OD ±0.003 mm, roundness 0.002 mm, Ra 0.2 µm
- Batch
- 150 pcs
Ground after coating; the coating is never the final dimension.
Mould insert
- Material
- Invar
- Size
- 80 × 60 × 25 mm
- Key callouts
- Flatness 0.003 mm, squareness 0.005 mm
- Batch
- 90 pcs
Surface ground on all six faces so the insert seats without shimming.
Gauge block set
- Material
- Invar
- Size
- 50 × 30 × 10 mm
- Key callouts
- Thickness ±0.002 mm, flatness 0.002 mm, parallelism 0.002 mm
- Batch
- 200 pcs
Ground wet in one chucking, then left to normalise before final inspection at 20 °C.
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 Grinding 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 Grinding
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 surface finish is achievable on Invar with CNC Grinding?
Grinding can take Invar to a fine finish — typically Ra 0.1–0.4 µm, and to a mirror grade on suitable alloys.
What tolerances can you hold for CNC Grinding Invar?
Achievable tolerances for Invar grinding depend on the alloy, geometry and feature size. Grinding routinely holds single-micron tolerances on diameter, flatness and parallelism. Exact figures are confirmed against your drawing callouts.
Can VT machining make custom Invar parts to my drawing?
Yes. Invar Invar grinding 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.
How clean are the edges produced by CNC Grinding on Invar?
Machined Invar edges are clean and to specification; edge-break or deburring is added when your drawing calls for it.