CNC Boring Invar from VT machining delivers precision Invar parts produced to your exact drawing. Boring enlarges and finishes existing holes to precise diameter, roundness and surface finish, and we tune every parameter to the behaviour of Invar, which is ultra-low thermal expansion.
Starting Parameters for CNC Boring Invar
| Cutting speed (carbide) | 35-75 m/min |
|---|---|
| Feed | 0.042-0.126 mm/rev |
| Spindle speed, Ø30 mm bore | 370-800 rpm |
| Insert / tool class | ISO S — sharp PVD-coated carbide |
| Coolant | Flood emulsion; sulphurised oil for tapping |
Shown for Invar 36, the most common Invar grade we see for CNC Boring. Starting values for Invar 36, Annealed; optimised on the first article.
CNC Boring Capability for Invar
- Bore tolerance to IT6
- Roundness within 0.005 mm
- Fine boring heads
- Large-diameter capability
Invar material properties, finishing options and grade notes are on our CNC Turning Invar page.
How CNC Boring Invar Works
The Invar bar or billet rotates in the spindle while single-point tools shape outer diameters, bores, faces, grooves and threads. Constant surface speed control keeps cutting conditions stable from large to small diameters.
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 Boring Invar
| Feature | Standard | Precision |
|---|---|---|
| Outside diameter | ±0.05 mm | ±0.005 mm |
| Bore diameter | H9 | H6 |
| Length / shoulder position | ±0.10 mm | ±0.020 mm |
| Concentricity OD to ID | 0.05 mm TIR | 0.010 mm TIR |
| Roundness | 0.02 mm | 0.005 mm |
| Thread class | 6g / 2A | 4h / 3A |
| Surface finish, as turned | 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.
Design Tips for CNC Boring Invar
Small design adjustments often cut cost and lead time. Consistent diameters, standard thread forms and avoiding extremely long, slender features help Invar turned parts stay concentric and economical. If you send your model early, we will return practical DFM feedback before you commit to production.
CNC Boring Tolerances & Surface Finish
Turned Invar holds diameter tolerances to about ±0.005 mm with concentricity within 0.01 mm and good roundness. Turned finishes of Ra 0.4–0.8 µm are achievable with finishing passes and sharp tooling.
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 Boring Invar
Invar parts made this way are found throughout aerospace, medical, automotive, electronics and industrial equipment. Prototype, bridge and production volumes are all welcome.
Typical Invar Parts for CNC Boring
Illustrative examples of CNC Boring Invar parts and the callouts that usually drive the process plan. They show the kind of work that fits this process; they are not specific customer orders.
Connector pin
- Material
- Invar
- Size
- Ø3.0 × 24 mm
- Key callouts
- OD ±0.005 mm, straightness 0.02 mm over length
- Batch
- 20,000 pcs
Swiss-turned from bar with a guide bushing; nothing else holds Ø3 mm over 24 mm.
Threaded fitting
- Material
- Invar
- Size
- Ø22 hex × 38 mm
- Key callouts
- G3/8" thread class 4h, bore H8, sealing face Ra 0.8 µm
- Batch
- 2,500 pcs
Run on a sub-spindle lathe so the back face is finished without a second setup.
Precision shaft
- Material
- Invar
- Size
- Ø16 × 240 mm
- Key callouts
- OD h6, concentricity 0.01 mm TIR, keyway 5 H9
- Batch
- 1,000 pcs / year
Turned between centres so both journals share one datum.
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 Boring 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 Boring
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
Does CNC Boring Invar require dedicated tooling?
Most Invar turning work uses standard cutting tools and CNC programs; dedicated fixtures are made only when geometry or volume requires them.
Why is Invar a good choice for CNC Boring?
Invar is ultra-low thermal expansion, which makes it well suited to CNC Boring. We tune the process to the alloy so the finished Invar turning part meets your dimensional and functional requirements.
Which industries use CNC Boring Invar parts?
CNC Boring Invar parts are used across aerospace, medical, automotive, electronics, semiconductor and general industrial sectors — anywhere precise Invar components are required.
What is CNC Boring Invar and how is it done?
CNC Boring Invar refers to boring enlarges and finishes existing holes to precise diameter, roundness and surface finish. 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.