A quote for a machined part can look complete while leaving one important question unanswered: what inspection evidence must arrive with the first shipment? For U.S. buyers sourcing overseas, defining the CNC first article inspection report before purchase order release helps prevent disputes about drawing revisions, critical dimensions, measurement methods, and approval status.
This guide explains what to request, what to place on the RFQ, and how to keep the inspection package proportional to part risk. It applies to custom CNC machined parts, tooling components, prototypes, and low-volume production. It does not assume that every order needs an aerospace-style report.
What Is a CNC First Article Inspection Report?
A first article inspection report records whether a part made by the planned manufacturing process conforms to the released drawing and purchase requirements. Depending on the order, the report may cover every drawing characteristic, selected critical features, material documentation, finishing requirements, and visual checks.
The words “first article” do not automatically define the format. A supplier’s standard dimensional report, a full characteristic-by-characteristic FAI, an AS9102 package, and an automotive PPAP submission are different deliverables. State the required format at the RFQ stage. SAE’s current AS9102C standard, for example, establishes aerospace first article inspection requirements; it should only be requested when it is contractually appropriate.
When Should a Buyer Request First Article Inspection?
The inspection effort should match the commercial and technical risk. A documented first article is commonly useful when:
- A new part number is being manufactured for the first time.
- The drawing, model, material, heat treatment, coating, or critical tolerance has changed.
- Production moves to a different supplier, machine, fixture, or manufacturing route.
- A replacement tooling component must match an existing assembly or mating part.
- A prototype is about to move into repeat production.
- The purchase order or customer quality plan requires formal approval before the remaining quantity is produced or shipped.
For a simple low-risk component, a report covering selected dimensions may be enough. For a complex or regulated part, the buyer may require full traceability, a ballooned drawing, certificates, and a prescribed approval form. The supplier cannot price the correct workload unless that scope is visible in the RFQ.
Eight Items Every Inspection Requirement Should Define
1. Drawing and Model Revision
Identify the controlling drawing number and revision, the 3D model revision, and any engineering change notices. If the 2D drawing and model disagree, the RFQ should say which one controls. The report should repeat the same part number and revision so that results cannot be separated from the specification they verify.
2. Ballooned Characteristics
A ballooned drawing assigns a unique number to each characteristic. The same numbers should appear in the results table beside the nominal value, limits, actual reading, and acceptance result. This makes the report auditable and prevents ambiguous entries such as “diameter OK.”
3. Datums and Measurement Setup
A measured value is meaningful only when it is tied to the correct datum structure and part condition. Define functional datums, alignment method, free-state or restrained condition, and any temperature or stabilization requirement that matters. This is especially important for thin parts, long components, tight positional tolerances, and features measured after heat treatment or coating.
4. Actual Values, Not Only Pass/Fail
For dimensional characteristics, request recorded actual values unless a go/no-go result is genuinely sufficient. Actual readings help the buyer review process centering, compare future lots, and identify dimensions drifting toward a limit. A report showing only “PASS” provides less useful evidence.
5. Measurement Method
The instrument should suit the feature, tolerance, access, and required uncertainty. A micrometer may be appropriate for an outside diameter; an optical system can help with small profiles and edges; a height gauge can evaluate features from a reference surface; and a CMM may be needed for three-dimensional relationships. Do not specify an instrument only by habit—define the characteristic and acceptance need first.
SkyPu’s inspection area includes Nikon optical measurement equipment and a TESA height gauge. The suitable method still depends on the part geometry, datum strategy, surface condition, and tolerance. Buyers should identify any required instrument, report format, or third-party inspection before quotation.
6. Material, Heat Treatment, and Finish Evidence
If the order requires material certificates, hardness results, coating certificates, or heat-treatment records, list them as separate deliverables. Dimensional conformity alone does not confirm alloy, hardness, plating thickness, or treatment condition. Also clarify whether final dimensions are inspected before or after coating.
7. Sampling and Quantity
State whether the report covers one piece, multiple cavities, one part from each setup, or a defined sample from the first lot. Also define whether production may continue before approval. “First article required” without a quantity or hold point can lead to avoidable schedule disagreements.
8. Approval and Nonconformance Rules
Name the person or function authorized to approve the report and define what happens when a result is outside the limit. A supplier should not alter the drawing, average unacceptable results, or ship under deviation without written buyer authorization. If a concession process exists, include it in the purchase requirements.
Metric and Inch Tolerances: Avoid False Precision
International RFQs often include both millimeters and inches. Use one controlling unit and treat the other as a reference conversion. Rounding can make a converted limit appear tighter or looser than the original requirement.
| Drawing tolerance | Approximate inch equivalent | Buyer note |
|---|---|---|
| ±0.010 mm | ±0.00039 in | Confirm datum, feature type, and measuring method. |
| ±0.005 mm | ±0.00020 in | Identify only the features that truly need this tolerance. |
| ±0.001 mm | ±0.00004 in | Requires feature-specific feasibility and measurement review. |
A blanket ±0.001 mm (about ±0.00004 in) requirement can increase machining and inspection cost without improving function. Apply very tight limits only to features that need them, then confirm the measurement method. For more detail, read CNC Machining Tolerances: How to Specify Them for an Accurate Quote.
What a Useful Results Table Looks Like
A practical results table should allow an engineer who has never seen the part to understand what was checked. At minimum, include:
- Part number, revision, purchase order, lot or job number, and inspection date.
- Balloon or characteristic number linked to the drawing.
- Characteristic description, nominal value, upper and lower limits.
- Actual measured result with the same unit as the controlled drawing.
- Instrument or measurement method where relevant.
- Pass/fail status and a clear reference to any approved deviation.
- Inspector identification and approval status.
Photographs can support traceability, but they do not replace measured results. Likewise, a machine photo does not prove dimensional conformity. The inspection package should connect the released specification, the manufactured item, and the recorded evidence.
How to Put Inspection Requirements in a CNC RFQ
Do not wait until the parts are ready to ship. Include inspection requirements with the drawing package so the supplier can review access, fixturing, measurement time, reporting effort, and outside-laboratory needs before quoting.
- Send the released 2D drawing and 3D model. See how to prepare CAD files for a CNC machining quote.
- Mark critical characteristics and functional datums instead of applying the tightest tolerance everywhere.
- Specify the report type: selected-dimension report, full ballooned FAI, customer template, AS9102, PPAP, or another defined format.
- List required certificates for material, heat treatment, coating, hardness, or outside testing.
- State sample quantity, production hold point, approval contact, and required delivery format.
- Confirm whether metric or inch units control and whether actual values are mandatory.
- Include packaging, labeling, and shipment traceability requirements.
Questions to Ask a CNC Supplier Before Ordering
- Will you review the drawing, datum scheme, and inspection scope before confirming the quote?
- Which characteristics cannot be measured reliably with the proposed method?
- Will inspection occur in the final material and finish condition?
- Can the report link each result to a ballooned drawing characteristic?
- How are part revision, lot identity, and inspection records controlled?
- Will production continue before first article approval, or will the order be placed on hold?
- How are nonconforming results reported and approved?
A supplier should be willing to identify unclear requirements before manufacturing begins. For a broader supplier-screening process, use our buyer’s checklist for choosing a CNC machine shop in China.
CNC First Article Inspection RFQ Checklist
- Part number and current revision
- 2D drawing and 3D model
- Material specification and condition
- Heat treatment, hardness, and surface finish
- Critical dimensions and functional datums
- Controlling unit: mm or inch
- Inspection report format and required template
- Ballooned drawing requirement
- Sample quantity and lot definition
- Required measurement methods or approved alternatives
- Material and process certificates
- Approval hold point and response deadline
- Deviation and nonconformance procedure
- Packaging, labeling, and shipping documentation
Frequently Asked Questions
Is a dimensional inspection report the same as a first article inspection report?
Not necessarily. A standard dimensional report may cover selected features. A first article package may require all drawing characteristics, revision accountability, material and process records, and formal approval. Define the deliverable instead of relying on the name.
Does every CNC part need a full first article inspection?
No. The scope should reflect part risk, application, order value, regulatory requirements, and the cost of failure. A selected-dimension report may be suitable for some low-risk orders, while other parts require complete documentation.
Should actual measurements be reported in both mm and inches?
Usually one unit should control. Dual-unit reporting can be supplied when needed, but the conversion and rounding rule must be clear. Recording results in the drawing’s controlling unit reduces ambiguity.
Can a supplier guarantee ±0.001 mm on every feature?
That tolerance is not realistic as a blanket promise. Capability depends on feature size, geometry, material, process sequence, thermal condition, fixturing, and measurement method. Each critical feature should be reviewed individually.
When should AS9102 or PPAP be specified?
Specify the exact standard or customer template when your contract, industry, or internal quality system requires it. Do so before quotation because the documentation and approval workload differs significantly from a basic inspection report.
Send Your Drawing and Inspection Requirements
SkyPu provides custom CNC precision machining for parts made to customer drawings. Send the released drawing, model, material, quantity, critical tolerances, and required inspection package for review.
Request an RFQ: upload your files through the contact page or email Lily@ksskypu.com. We will review the manufacturability and inspection requirements before confirming the quotation.
