Drawings override defaults
These defaults apply only where your drawing is silent. Dimensional callouts, GD&T, thread specs, and surface-finish symbols on your 2D drawing always override the defaults above. Tighter tolerances than the precision limits are subject to engineering review based on part geometry, material grade, and tool access; temperature-controlled machining is available for precision aerospace components.
Default Tolerances
| Feature | Standard | Precision / Limit |
|---|---|---|
| CNC milling — linear dimensions | ±0.050 mm (±0.002") ISO 2768-m (Fine) | ±0.010 mm (±0.0004") |
| CNC turning — linear dimensions | ±0.050 mm (±0.002") ISO 2768-m (Fine) | ±0.010 mm (±0.0004") |
| Swiss-type lathe | ±0.025 mm (±0.001") Precision lathe spec | ±0.005 mm (±0.0002") |
| Wire EDM | ±0.005 mm (±0.0002") Ultra-precision spec | ±0.005 mm (±0.0002") |
| Minimum feature size | 0.5 mm milling / 0.3 mm turning | 0.1 mm Swiss lathe / 0.05 mm wire EDM |
| Maximum part size (milling) | 2,000 × 1,000 × 800 mm | Turning: 1,500 mm length × 800 mm dia. |
* Values match the specification tables on our CNC Machining service page. Tighter requirements are reviewed per part.
Finish Expectations
| Finish | Specification | What to Expect |
|---|---|---|
| As-milled (standard) | ISO 1302 (standard machined) | Ra 3.2 µm (125 µin) standard; Ra 1.6 µm or 0.8 µm options. Visible tool marks; best for internal structural components. |
| Anodizing Type II (clear/color) | MIL-A-8625, Type II, Class 1/2 | Corrosion protection and decorative color; maintains base roughness. |
| Anodizing Type III (hardcoat) | MIL-A-8625, Type III, Class 1/2 | Thick, wear-resistant coating; slightly increased friction. For sliding rails, gears, hydraulic cylinders. |
| Chem film (Alodine) | MIL-DTL-5541, Type I/II | Chemical conversion coating; corrosion protection while maintaining electrical conductivity. No change to dimensions. |
| Passivation | ASTM A967 / AMS 2700 | Chemical treatment for stainless steel; removes free iron to prevent rust. No change to dimensions. |
| Electropolishing | ASTM B912 | Ra ≤ 0.4 µm (mirror shine); removes microscopic peaks for a clean, high-purity surface. |
| Bead blasting / tumbling | Industry standard (glass bead) | Uniform matte texture; removes minor tool marks. Preparation for paint or coatings. |
Edges, Burrs & Cosmetic Surfaces
The default as-milled finish shows visible tool marks (Ra 3.2 µm standard). Bead blasting or tumbling removes minor tool marks and produces a uniform satin appearance. Critical edge breaks, chamfers, and deburr requirements should be called out on your drawing — drawing callouts always govern.
Inspection Options
- Dimensional inspection with CMM reports included with every order
- First Article Inspection (FAI)
- PPAP documentation and FMEA
- AQL-based sampling for production runs
- Pre-shipment gate: CMM testing, optical gauging, thread go/no-go matching, roughness profiling
- Material Mill Test Reports (MTR) and certificate-of-conformity logs on request
Full detail on inspection tiers and documentation is on our Quality Hub.
Vietnam Network Notes
DEWIN maintains relationships with 50+ audited CNC facilities across Vietnam running Haas, Mazak, and Fanuc machining centers, DMG Mori and Hermle 5-axis centers, Citizen and Star Swiss lathes, and Sodick and Mitsubishi EDM machines. Vietnamese CNC parts are not subject to US Section 301 tariffs (25% applies to Chinese equivalents).
Typical Lead Times
| Scope | Lead Time |
|---|---|
| CNC milling | 5–15 business days |
| CNC turning | 5–15 business days |
| Swiss-type lathe | 10–20 business days |
| Wire EDM | 7–15 business days |
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