First Article Inspection Checklist for Turned Parts: A Quality Engineer's Guide

A first article inspection checklist for turned parts is a structured, balloon-referenced list of every design characteristic on a CNC lathe component—diameters, lengths, threads, runout, surface finish, and material certification—that must be measured and documented on the first production piece before volume release. It maps directly to AS9102 Rev C Form 3 and ensures no drawing requirement is skipped.

When a Single Missed Dimension Grounds a Delivery

A shaft arrives at goods-in. The purchase order calls for an FAI. The supplier sends a report with 47 of 48 characteristics filled in. The missing one? The minor diameter of an M20×2.5 thread on a hydraulic valve body. The whole batch goes on hold.

That scenario is not unusual. Turned parts carry more individual geometric characteristics per cubic centimetre than almost any other machined form—multiple diameters, lengths, chamfers, undercuts, thread classes, runout callouts, and surface finish requirements stacked onto a single spindle setup. A checklist built specifically for turned components stops those gaps before they become NCRs.

What Is Actually at Stake

FAI requirements for CNC turned components exist because a lathe program verified in simulation can still produce an out-of-tolerance part in production. Tool wear, bar stock straightness, chuck jaw condition, and thermal growth all shift dimensions. The FAI is the first hard evidence that the production process—not just the program—is capable.

Failing an FAI late, after the customer receives parts, triggers corrective action, potential 8D reports, and possible supplier derating. In aerospace under AS9102, an incomplete FAI is a non-conformance against the purchase order quality clause. In automotive, a missing PPAP dimensional results sheet can suspend a supplier code. The paperwork is inseparable from the part.

The Complete Checklist for Turned Parts

Work through these sections in order. Each maps to a specific AS9102 Rev C form or a supporting document. For a full breakdown of the three forms, see the guide on AS9102 Forms 1, 2 & 3 Explained.

Section 1 — Documentation Review (AS9102 Form 1)

1. Confirm drawing revision. Record the exact revision letter and date. Any discrepancy between the drawing on file and the drawing used for machining is an immediate stop.
2. Verify part number and serial/lot number traceability. The report part number must match the purchase order and the physical part marking exactly, including dash numbers.
3. Check applicable specifications. List every referenced standard on the drawing face—ASME Y14.5-2018 for GD&T, applicable thread standards (ASME B1.13M for metric, ASME B1.1 for Unified), and any customer-specific quality clauses.
4. Confirm general tolerance standard. Most precision turned parts call out ISO 2768-m or ISO 2768-f in the title block. Untoleranced dimensions default to that class—record which one applies.
5. Record material specification. For aerospace this typically means an AMS or ASTM material number. The material cert must match the drawing callout exactly.

Section 2 — Material and Process Certification (AS9102 Form 2)

1. Obtain and attach the material test report (MTR). Verify heat number, chemical composition, and mechanical properties against the drawing material callout.
2. Verify hardness if specified. A drawing calling 28–34 HRC requires a traceable hardness test result, not just a heat treat certificate.
3. Confirm special process certs. Plating, anodising, passivation per ASTM A967, or black oxide—each needs a signed processor certificate with the processing date.
4. Check calibration status of gauges. Every gauge used must have a valid calibration certificate traceable to NIST or an equivalent national standard. Record the gauge ID and calibration due date in the report.

Section 3 — Balloon the Drawing

Before measuring anything, balloon every characteristic and assign a sequential number. This is non-negotiable under AS9102 Rev C—each balloon number becomes a row on Form 3. Skipping this step is the single most common reason FAI reports are rejected.

For turned parts, the balloon count is often higher than expected. A simple shaft with six diameters, four length dimensions, two chamfers, one thread, two runout callouts, a surface finish symbol, and a concentricity frame can easily reach 20–25 balloons before adding general tolerance characteristics.

CadNexa's Smart Detect Dimensions feature scans the whole drawing in one click and auto-detects dimensions, tolerances, and GD&T frames for review—cutting balloon setup time significantly on dense turned-part drawings. Once balloons are placed, the FAI Report Generator builds Form 3 rows automatically from the balloon data.

Section 4 — Dimensional Results (AS9102 Form 3)

This is the core of the FAI. Work through every ballooned characteristic systematically.

Diameter and Length Dimensions

1. Measure each turned diameter at a minimum of two cross-sections and two axial positions. Record the worst-case reading as the actual value. For features wider than 25 mm, add a third cross-section.
2. Use the correct gauge for the tolerance band. A ±0.05 mm tolerance accepts a 0.01 mm resolution micrometer. A ±0.005 mm tolerance requires a 0.001 mm resolution bench micrometer or air gauge. Using a vernier calliper on a tolerance tighter than ±0.05 mm is a gauge adequacy failure.
3. Record nominal, upper limit, lower limit, and actual. The AS9102 Form 3 column structure requires all four values. A result logged only as "pass" is non-conforming to the standard.

Thread Characteristics

1. Verify thread form with go/no-go gauges. Record the gauge designation, tolerance class (e.g., 6H/6g for metric, 2B/2A for Unified), and result. The go gauge must pass; the no-go gauge must not enter.
2. Check pitch diameter if the drawing calls a tighter-than-standard tolerance class. A thread designated M16×2–5H6H requires a thread measuring wire set or CMM stylus measurement of pitch diameter.
3. Confirm thread length. It is a separate balloon from the thread callout and is frequently missed.

GD&T Characteristics

1. Runout (circular and total). Support the part between centres or in a precision V-block. Rotate 360°. Record full indicator movement (FIM). Circular runout applies at each cross-section; total runout applies across the full feature length. See the detailed post on Runout vs Total Runout for measurement setup guidance.
2. Concentricity/coaxiality. Establish the datum axis first. Measure derived median points—this requires a CMM, not a dial test indicator. Using a DTI to "measure concentricity" is a method error under ASME Y14.5-2018.
3. Perpendicularity of faced ends. Fixture the part on the datum bore or OD. Sweep a DTI across the face. Record the worst reading as the perpendicularity value.
4. True position of cross-holes. Establish X, Y deviation from nominal using CMM or an optical comparator. Calculate true position: TP = 2 × √(ΔX² + ΔY²). For a worked example, see the post on GD&T True Position Formula.

Surface Finish

1. Measure Ra with a contact profilometer. Align the stylus perpendicular to the lay direction (parallel to the turning axis for cylindrical surfaces). Take three readings and record the average.
2. Confirm the correct parameter. Some drawings specify Rz or Rmax rather than Ra—especially older ISO 1302 callouts. Measuring Ra when Rz is specified is an incorrect measurement even if the number looks acceptable.
3. Use comparator plates only for non-critical surfaces where the drawing explicitly permits visual comparison.

Reference Table — Typical Characteristics on a Turned Part FAI

Section 5 — Visual and Cosmetic Inspection

1. Check for burrs, sharp edges, and tool marks against the drawing's edge break callout (e.g., "break all sharp edges 0.2–0.5 mm").
2. Verify part marking. Many aerospace and medical drawings require part number, revision, and material mark to be electro-etched or laser marked. Check location, character height, and depth against the drawing note.
3. Inspect for surface defects. Chatter marks, built-up edge deposits, and micro-cracks on ground surfaces are rejection criteria regardless of dimensional conformance.

Section 6 — Report Compilation and Sign-Off

1. Compile Forms 1, 2, and 3 into a single FAI package. Every row on Form 3 must have a result—blank cells are not acceptable.
2. Flag any out-of-tolerance characteristics. Record the actual value, mark the row as non-conforming, and attach a disposition (rework, scrap, or customer deviation request).
3. Sign and date by the authorised quality representative. AS9102 Rev C requires sign-off by a person with delegated authority—typically the Quality Manager or a designated quality engineer.
4. Submit with supporting evidence. Attach the material cert, process certs, gauge calibration certificates, and any CMM printouts. A report without evidence is incomplete and rejectable.

Common Mistakes on Turned Part FAIs

• Measuring diameter at only one plane. A barrel-shaped or tapered bore passes a single-plane check but fails a two-plane measurement. Always measure at two axial positions minimum.
• Omitting untoleranced characteristics. ISO 2768-m still requires inspection of untoleranced features. If it appears on the drawing, it needs a balloon and a measurement.
• Confusing datum setup between runout and concentricity. Runout is measured with a DTI rotating about the datum axis. Concentricity requires derived median points via CMM—a DTI-based approach is a method error under ASME Y14.5-2018.
• Using an uncalibrated gauge. A calibration sticker expired by even one day invalidates every measurement taken with that instrument. Check the due date before starting any measurement session.
• Submitting Form 3 without balloon numbers on the drawing. The customer cannot verify which measurement corresponds to which feature without a ballooned drawing attached. This is a documentation non-conformance, not merely an administrative oversight.
• Recording "per drawing" instead of a numeric actual. AS9102 Form 3 requires a numeric actual result in every row. "Per drawing" or "OK" are not acceptable entries.

For a broader look at documentation errors across standards, the AS9102 vs PPAP comparison post is worth reading before your next submission.

How CadNexa Helps Quality Engineers with Turned Part FAIs

CadNexa's FAI Report Generator builds AS9102 Rev C Forms 1, 2, and 3 directly from the ballooned drawing—no copy-pasting dimension values into a spreadsheet. The Box+Balloon OCR reads diameter values, tolerance bands, thread callouts, and GD&T frames from the PDF drawing and pre-fills each balloon row. Once measurements are entered, the report exports as interactive HTML, PDF, or CSV for submission or archiving.

For a turned part with 40 ballooned characteristics, Form 3 is structured and numbered before the first measurement is taken—which eliminates the most common FAI rejection cause. Try it on your next turned part drawing at cadnexa.com/app.html.

Frequently Asked Questions

What is a first article inspection checklist for turned parts?

A first article inspection checklist for turned parts is a structured, balloon-referenced list of every design characteristic on a CNC lathe component—diameters, lengths, threads, runout, surface finish, and material certification—that must be measured and documented on the first production piece before volume release. It maps directly to AS9102 Rev C Form 3 and ensures no drawing requirement is skipped.

Which AS9102 forms apply to CNC turned components?

All three AS9102 Rev C forms apply. Form 1 captures design documentation and part traceability. Form 2 records material and special process certifications. Form 3 is the dimensional results sheet where every ballooned characteristic is measured and recorded against its nominal and tolerance. For a field-by-field breakdown, see AS9102 Forms 1, 2 & 3 Explained.

How many parts must be measured for an FAI on a turned component?

AS9102 Rev C requires the inspection of one part unless the customer specifies otherwise. PPAP typically requires five parts for dimensional results. Always check the purchase order quality clause—some aerospace primes require five-piece FAIs even on single-cavity turned parts.

What tolerances apply to turned features not explicitly toleranced on the drawing?

Untoleranced linear dimensions on machined parts typically default to ISO 2768-m (medium) or the general tolerance note in the drawing title block. Confirm which class applies before measuring—assuming an unstated class is an auditable error under AS9102.

Can I use CadNexa to generate an AS9102 FAI report for turned parts?

Yes. CadNexa's FAI Report Generator creates AS9102 Rev C Forms 1, 2, and 3 directly from ballooned drawing data. The Box+Balloon OCR pre-fills dimension values, tolerances, and GD&T frames automatically. Export the completed report as interactive HTML, PDF, or CSV.

Conclusion

A well-executed FAI on a CNC turned component is the earliest possible proof that the production process is capable of holding the drawing. The checklist above covers documentation, material certification, dimensional results for every characteristic type common to lathe parts, and the sign-off requirements under AS9102 Rev C.

Work through the sections in order, balloon every characteristic before measuring anything, and record numeric actuals for every row. That discipline alone eliminates the majority of FAI rejections seen in practice.