Invar 36 Machining Services
Precision parts in 4J36 / ASTM F1684 / UNS K93603 — machined with a drift-control process developed for the applications where thermal stability is the whole point.
Flatness < 0.01 mm on 200 mm sections
ZEISS CMM report with every order
Prototype in 5–7 working days
What we make from Invar 36
Invar 36’s near-zero thermal expansion (≈1.2 × 10⁻⁶/K from 20–100 °C) makes it the default choice wherever a structure must not grow or shrink. We machine it into:
- Semiconductor & metrology structures — frames, stages, brackets and reference blocks for inspection equipment
- Optical & laser assemblies — mounts, barrels and housings where micron-level alignment must survive temperature change
- Aerospace composite tooling — cure tooling that keeps its shape through autoclave cycles (civil applications)
- Scientific instruments — interferometry fixtures, cryogenic supports, laboratory reference components
- Electronics packaging — housings and carriers paired with Kovar or glass substrates
Why most shops fail at Invar — and how we control it
Invar 36 is not hard to cut. It is hard to cut and keep straight. Two behaviors defeat general machine shops:
1 · Heat goes in, never out
Because Invar barely expands, cutting heat does not dissipate through growth — it accumulates as localized stress. A part that measures perfect at the machine drifts a week later on the buyer’s CMM.
2 · Residual stress redistributes
Mill-supplied bar carries rolling and drawing stresses. Roughing unbalances them, and thin walls or deep pockets spring. The classic symptom: a flat part bows after pocketing.
3 · Our countermeasures
Aggressive roughing with generous leave-on-stock → stress-relief anneal → re-datum → light, sharp, flood-cooled finishing passes → 20 °C soak before ZEISS inspection. Sequence is engineered per part, not improvised.
Specifications & capabilities
| Parameter | Capability |
|---|---|
| Material designations | Invar 36 / 4J36 / ASTM F1684 / UNS K93603 / 1.3912; Invar 36 free-machining variants on request |
| General tolerance | ISO 2768-m, or per your drawing |
| Precision tolerance | ±0.02 mm standard · ±0.002 mm capability · ±0.001 mm on selected features |
| Flatness / parallelism | < 0.01 mm over 200 mm sections (process-dependent, quoted per drawing) |
| Surface finish | Ra 0.8 µm standard finishing; Ra 0.4 µm or better on request |
| Part size range | From 2 mm features to 600 mm envelope (larger on request) |
| Processes | 5-axis milling, CNC turning, wire EDM (Sodick/GF+), surface & OD grinding, jig boring |
| Inspection | ZEISS CMM at 20 °C, FAI dimensional report against GD&T with every shipment |
| Documentation | Mill test certificate (EN 10204 3.1), FAI dimensional report, process traceability; PPAP-style documentation on request |
| MOQ | None — prototypes welcome |
Frequently asked questions
What tolerances can you hold on Invar 36 parts?
±0.02 mm on general features, ±0.002 mm (down to ±0.001 mm on selected features) on critical dimensions. Flatness and parallelism are controlled through stress-relief sequencing and temperature-controlled inspection at 20 °C.
Why does Invar 36 move during machining?
Invar 36’s near-zero thermal expansion means cutting heat accumulates as stress instead of dissipating, and residual stresses from roughing redistribute in thin sections. We counter it with aggressive roughing, stress-relief annealing between operations, light sharp-tool finishing and controlled-temperature inspection.
Do you provide material certificates?
Yes — mill test certificates and FAI dimensional reports from our ZEISS CMM ship with every order. Chemical composition certificates are available on request.
What is your minimum order quantity?
None. We regularly machine one-off prototypes and pre-production runs, and scale to batch production once your design is validated.
Can you also supply Kovar or hybrid Invar/Kovar assemblies?
Yes — see our Kovar machining page. We machine both alloys and can assemble hybrid packages with controlled fit.
Send us your Invar 36 drawing
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