Manufacturing Standards
Manufacturing Standards
Typical default tolerances and workmanship expectations that apply when your drawing does not specify otherwise. Your drawing and the accepted quote always take precedence.
Precedence
What governs your parts
Your drawing
Dimensions, tolerances, GD&T, finishes, and notes on a supplied 2D drawing govern.
The accepted quote
Requirements agreed on the quote, such as inspection, certificates, and finish specs.
These defaults
Typical defaults below apply only where neither the drawing nor the quote specifies a requirement.
CNC Machining
Machined parts
| Item | Typical default unless specified |
|---|---|
| General tolerances, metals | ISO 2768-m (medium); e.g. ±0.1 mm for 3–6 mm, ±0.2 mm for 6–30 mm, ±0.3 mm for 30–120 mm features |
| General tolerances, plastics | ISO 2768-m or looser by review; plastics move with temperature and moisture |
| Geometric tolerances | ISO 2768-K for features without callouts |
| As-machined surface roughness | About Ra 3.2 µm (125 µin); tool marks visible |
| Edges | Sharp edges broken and deburred; specify edges that must stay sharp |
| Threads | Per drawing callout; modeled threads without callouts are clarified during review |
ISO 2768-m example values are from the standard’s linear tolerance table. Tighter tolerances are available when shown on the drawing and confirmed on the quote.
Sheet Metal
Sheet metal and cut parts
| Item | Typical default unless specified |
|---|---|
| Cut edge to edge (laser/waterjet) | About ±0.1–0.2 mm (±0.005–0.008 in) |
| Bend to edge or hole | About ±0.25–0.4 mm (±0.010–0.015 in) |
| Bend angle | About ±1° |
| Across multiple bends | Tolerances accumulate; dimension critical features from one datum |
| Material thickness | Per mill stock tolerance |
| Flatness | Not guaranteed on cut sheet unless specified |
3D Printing
Additive parts
| Process | Commonly published typical accuracy |
|---|---|
| FDM | About ±0.3–0.5% (lower limit ~±0.2–0.5 mm) |
| SLA | About ±0.1–0.2% (lower limit ~±0.05–0.15 mm) |
| SLS / MJF | About ±0.3% (lower limit ~±0.3 mm) |
| Metal (DMLS/SLM) | About ±0.1–0.2 mm for small features; post-machining for critical fits |
Accuracy depends on geometry, orientation, material, and post-processing. Printed threads and precision bores are typically finished by tapping or machining.
Molding and Casting
Molded and cast parts
Injection molding
Typical tolerances depend on material shrink and part size; critical dimensions are reviewed with the tool design and first-article samples.
Urethane / vacuum casting
Typically about ±0.15–0.3% due to silicone mold and resin shrink.
Die casting
As-cast tolerances depend on alloy and size; critical features are often post-machined.
Draft and parting lines
Parting lines, gate vestiges, and ejector marks are normal unless restricted on the drawing.
Cosmetic Standards
Workmanship and appearance
Surfaces
Free of chips, burrs, cutting fluid, and handling damage; minor tool marks acceptable on non-cosmetic surfaces.
Cosmetic faces
Identify cosmetic surfaces and acceptable defect levels on the drawing.
Coatings
Uniform coverage on coated surfaces; masked areas per drawing.
Supports and witness marks
Printed and molded parts may show support or gate marks unless secondary finishing is requested.
Need Tighter Specs?
Put requirements on your drawing.
Call out tolerances, GD&T, finishes, and inspection needs so they are reviewed and quoted.