Default Workmanship
CNC Machining Manufacturing Standards
These standards describe The following screening default requirements when the approved drawing or purchase order does not specify otherwise. Customer-approved specifications take precedence. Tight tolerances, cosmetic criteria, special inspection and regulatory documentation must be agreed before quotation and production.
Document Priority and Revision Control
- Approved purchase order and formally accepted customer specification
- Approved 2D drawing and its revision
- Approved 3D model
- Agreed quotation and written clarification
- Formexi default manufacturing standards
If files conflict, production is paused until the customer confirms the controlling requirement.
Provisional Default Tolerances
| Requirement | Provisional standard | Condition |
|---|---|---|
| Unspecified dimensions | ISO 2768-m | Subject to engineering approval before formal publication |
| General metal dimensions | ±0.10 mm | Where size and geometry are suitable |
| General plastic dimensions | ±0.10 to ±0.20 mm | Depends on material stability, size and geometry |
| Routine precision feature | Approximately ±0.05 mm | Suitable material, geometry and measurement |
| Qualified tight feature | Down to ±0.01 mm | Not a blanket capability; specific review required |
These values must be approved by Formexi engineering and quality before being treated as contractual standards.
Surface Roughness
| Standard as-machined | Ra 3.2 μm unless otherwise specified and confirmed |
|---|---|
| Improved machined finish | Ra 1.6 μm or Ra 0.8 μm on suitable features |
| Ground finish | Project-specific; material, geometry and grinding method determine capability |
Visible tool marks may remain on as-machined surfaces. Cosmetic surfaces must be identified separately.
Edges, Burrs, Holes and Threads
- Loose burrs are removed and sharp machining edges are broken unless a functional edge must remain sharp.
- A provisional edge break of approximately 0.2–0.5 mm may be used where function permits.
- Deep holes, blind threads and small thread depths require review for tool access and effective engagement.
- Metric, UNC, UNF, BSP, BSPT and NPT threads are supported subject to drawing and gauge availability.
- Threads may be checked using go/no-go plug or ring gauges and dimensional methods as appropriate.
Geometry Requiring Specific Review
Metal walls below approximately 0.5 mm, plastic walls below approximately 0.8 mm, deep cavities, long slender shafts, hard materials and heat-treated parts may distort or require a special process. These figures are screening guides, not automatic acceptance criteria.
Appearance and Finishing
Buyers should identify A, B and C appearance surfaces on the drawing. Color, gloss, texture, masking and allowable visual defects should reference a specification or approved sample. Coating thickness can change holes, threads and mating dimensions and must be included in the design allowance.
Inspection and Packaging
Standard inspection combines sampling with verification of identified critical dimensions. Full-dimensional, CMM, FAI, material and finish documentation must be requested before ordering. Parts are cleaned, separated where needed, protected against corrosion or scratching and labeled to the approved order.
Standards and Regulatory Sources Used on This Page
For CNC Machining Manufacturing Standards, these primary sources define the scope of cited standards or regulations. They do not prove Formexi certification, a customer approval or project compliance; those require current, scope-matched records.
Have a Requirement Outside These Defaults?
Send the drawing and inspection specification before quotation so the correct process, cost and documentation can be confirmed.