CNC Tapping Invar is a core capability at VT machining. We combine controlled machining with material-aware setup for Invar — an alloy that is ultra-low thermal expansion — to produce parts that meet your specification first time.
Starting Parameters for CNC Tapping Invar
| Cutting speed (carbide) | 5-10 m/min |
|---|---|
| Recommended tap | Form (roll) tap — chipless |
| Tap drill for M8×1.25 | Ø7.4 mm (form tap) |
| Spindle speed, M8 | 200-400 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 Tapping. Starting values for Invar 36, Annealed; optimised on the first article.
CNC Tapping Capability for Invar
- Metric & UNC/UNF threads
- Rigid synchronized tapping
- Thread depth control
- Form and cut taps
Invar material properties, finishing options and grade notes are on our CNC Milling Invar page.
How CNC Tapping Invar Works
Rotating multi-flute cutters remove material as the Invar workpiece is driven through programmed tool paths on 3-, 4- or 5-axis machining centres. Climb milling, step-over and depth-of-cut are set so chip load stays in the ideal band for the alloy.
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 Tapping Invar
| 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.
Design Tips for CNC Tapping Invar
Small design adjustments often cut cost and lead time. Generous internal radii, sensible pocket depth-to-width ratios and avoiding very thin unsupported walls all reduce cost and improve accuracy in Invar. If you send your model early, we will return practical DFM feedback before you commit to production.
CNC Tapping Tolerances & Surface Finish
For CNC Tapping, 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.
Applications of CNC Tapping 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 Tapping
Illustrative examples of CNC Tapping 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.
Manifold block
- Material
- Invar
- Size
- 120 × 60 × 45 mm
- Key callouts
- Cross-bore intersection ±0.05 mm, ports G1/8", leak-tested to 10 bar
- Batch
- 80 pcs
Deburred internally with a brush tool; a burr at a cross-bore is what fails the leak test.
Heat sink base
- Material
- Invar
- Size
- 200 × 100 × 8 mm
- Key callouts
- Fin thickness 1.2 ±0.05 mm, base flatness 0.03 mm
- Batch
- 500 pcs
Fins cut with a slotting cutter in one pass to avoid the deflection a step-over leaves.
Optical mount plate
- Material
- Invar
- Size
- 160 × 160 × 12 mm
- Key callouts
- Hole pattern true position ±0.02 mm, flatness 0.01 mm
- Batch
- 40 pcs
Roughed, stress-relieved overnight, then finished — the plate is too thin to hold flatness in one hit.
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 Tapping 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 Tapping
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 Tapping Invar and how is it done?
CNC Tapping Invar refers to rigid CNC tapping cuts internal threads in sync with spindle feed for precise, repeatable thread engagement. 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.
What tolerances can you hold for CNC Tapping Invar?
Achievable tolerances for Invar 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.
Does CNC Tapping Invar require dedicated tooling?
Most Invar machining work uses standard cutting tools and CNC programs; dedicated fixtures are made only when geometry or volume requires them.
Can VT machining make custom Invar parts to my drawing?
Yes. Invar machining 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.