Invar 36 (UNS K93600) is a difficult-to-machine material that we run regularly for export customers. It has a density of 8.05 g/cm3, a tensile strength of 490 MPa and a typical hardness of HB 160. Those numbers make it the right choice for optical benches and laser housings, and a poor choice when cost or corrosion resistance matters more than mechanical performance.
On our machines we hold +/-0.02 mm on turned and milled features and reach Ra 1.6 um where the drawing calls for it. Standard lead time for Invar 36 parts is 4-8 working days, including material procurement, machining and any finishing operation you specify.
Invar 36: key properties
| Property | Value |
|---|---|
| UNS / designation | K93600 |
| Density | 8.05 g/cm3 |
| Tensile strength | 490 MPa |
| Hardness | HB 160 |
| Machinability | Difficult |
| Suggested cutting speed (carbide) | 80-120 m/min |
| Relative material cost | 5 of 5 |
Machining Invar 36: what to plan for
- Gummy, stringy chips
- Low thermal expansion makes it sensitive to warm-up
- High cost
Cutting speed for Invar 36 with carbide tooling sits around 80-120 m/min. Going faster burns the edge; going much slower causes rubbing and a poor surface. Flood coolant is not optional here. If your part has thin walls or a lot of stock to remove, say so in the RFQ — we plan roughing, stress relief and finishing as separate operations when the geometry demands it.
Parts we machine in Invar 36
- Optical benches
- Laser housings
- Metrology fixtures
- Composite tooling
Most Invar 36 work arrives as 2D drawings with a mix of critical and non-critical features. Loosening tolerance on the non-critical ones is the fastest way to cut cost, and we will tell you which features those are before we quote.
Tolerances, finish and lead time
| Item | Capability |
|---|---|
| General tolerance | +/-0.02 mm |
| Achievable surface finish | Ra 1.6 um |
| Minimum wall thickness | 0.8 mm (aluminium) / 1.0 mm (steel and stainless) |
| Typical lead time | 4-8 working days |
| Prototype quantity | 1 piece |
| Production quantity | 10 to 50,000 pieces |
Frequently asked questions
What is the lead time for Invar 36 parts?
Standard is 4-8 working days from drawing release, assuming the material is in stock. Exotic grades and cast forms can add 5 to 10 days. Finishing such as anodizing or plating adds 3 to 5 days.
What tolerance can you hold in Invar 36?
+/-0.02 mm is routine on turned and milled features. Tighter than that is possible on specific features by grinding or lapping, but it is quoted separately because it changes the process.
Do you keep Invar 36 in stock?
We hold common sizes of Invar 36 and buy mill-certified stock for everything else. Material certificates are supplied with the parts on request.
Can you supply Invar 36 parts with a certificate of conformity?
Yes. We issue a dimensional report, a material certificate and a certificate of conformity as standard for production orders, and full PPAP or AS9102 paperwork when the programme requires it.
Related pages
- Materials — the full index for this section.
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- Instant CNC quote
- Tolerance quick reference
- Frequently asked questions
Get a price for your part
Send a STEP file and a drawing with tolerances, material and quantity. We quote within one working day and machine in our own facility in Shenzhen — milling, turning, EDM, grinding and finishing under one roof, no trading middleman.
Start an instant quote or send your drawings directly. English-speaking engineering support, DFM feedback before you commit to a batch.