🔥 NADCAP
NADCAP Accredited Grinding: Special-Process Sourcing Guide
Here is the honest nuance most buyers miss: there is no standalone NADCAP checklist called "grinding." The accreditation that controls a ground aerospace part attaches to the special processes wrapped around the grind, and understanding that distinction is the difference between sourcing a compliant supplier and assuming a gap closed that never was.
NADCAPAS9100ISO 9001
What NADCAP Accredits Around a Grind, and What It Does Not
NADCAP (the National Aerospace and Defense Contractors Accreditation Program, run by the Performance Review Institute) accredits special processes against industry-consensus audit criteria written as Audit Criteria (AC) checklists and tied to the relevant Pyrometry and process specifications. The subscriber primes, GE Aviation, Boeing, Lockheed, Pratt and Whitney, Rolls-Royce, Honeywell, mandate NADCAP for the special processes their parts pass through.
Grinding itself is generally treated as a conventional machining operation, not a NADCAP special-process commodity in the way heat treatment or chemical processing are. What gets accredited is the cluster of special processes that determine whether a ground part is airworthy: heat treatment (AC7102) performed before grinding, chemical processing and plating (AC7108/AC7004) after, nondestructive testing (AC7114) such as fluorescent penetrant and magnetic particle, and critically the etch inspection used to detect grinding burn, which is audited under the chemical processing and surface-treatment criteria.
So when a prime says a ground turbine shaft requires NADCAP, they almost never mean the abrasive operation, they mean the burn-detection etch, the pre-grind heat treat, and the post-grind NDT and finishing. A buyer who reads "NADCAP grinding" as a single accreditation will look for the wrong certificate. The right question is which special processes touch your ground part and whether each is NADCAP-accredited.
Grinding Burn and the Etch-Inspection Connection
The reason NADCAP and grinding are linked in buyers' minds at all is grinding burn. When hardened steel is ground too aggressively, with a dull or glazed wheel, too high an infeed, or inadequate coolant, the surface heats enough to re-temper or re-harden, leaving residual tensile stress and microcracks that slash fatigue life on rotating hardware. The damage is often invisible to the eye.
The standard detection method is a controlled chemical etch, the nital etch (or temper etch) inspection per specifications like AMS 2649, where the part is etched in a sequence of acid and alkaline baths to reveal localized re-tempering or re-hardening as discoloration. Because this is a chemical process with strict bath control, solution concentration, temperature, immersion time, rinse, and operator interpretation, it falls under NADCAP's chemical processing and surface-treatment audit scope. Barkhausen noise analysis and X-ray diffraction for residual stress are alternative or supplementary methods, also performed under accredited control.
This is why an aerospace ground part typically routes through a NADCAP-accredited etch source after grinding. A supplier offering aerospace grinding without access to accredited burn inspection has a real, common gap, the grind may be dimensionally perfect and still metallurgically damaged with no proof either way.
Verifying Accreditation in eAuditNet
NADCAP accreditations are publicly verifiable in eAuditNet, the PRI's online system, which lists accredited suppliers by company, location, and specific commodity (HT for heat treat, CP for chemical processing, NDT, and so on). A buyer should look the supplier up by name and confirm the exact special-process commodities required for the ground part appear as accredited and current, accreditations are time-limited and must be renewed, with merit-based intervals that extend for strong performers and shorten for those with findings.
Verify the accreditation is for the specific facility doing the work, not a sister plant, and that the scope covers the specification your job calls out (for example, the AMS spec for the etch or the heat-treat process). A common failure is assuming a corporate NADCAP listing covers a satellite location or a process variant it does not. Also confirm the accreditation is active and not suspended, which eAuditNet reflects.
For a ground part, build a small map: pre-grind heat treat, the grind itself (covered by the shop's AS9100 quality system and the drawing), post-grind burn-etch inspection, any NDT, and final plating or coating. Each special-process box should trace to a current NADCAP accreditation, in-house or at a controlled subcontractor. That map is what actually proves the ground part is compliant, not a single certificate.
How NADCAP Sits on Top of AS9100
NADCAP and AS9100 are complementary layers, not alternatives, and aerospace ground parts generally need both. AS9100 certifies the supplier's overall quality management system, including the requirement (Clause 8.5.1.1) to validate and control special processes. NADCAP is how that requirement is satisfied for the specific processes the primes care about: it is the third-party, industry-managed accreditation that gives the AS9100 special-process control real teeth.
In practice, a prime's flowdown will require AS9100 at the system level and NADCAP for the named special processes. A grinding supplier therefore typically holds AS9100 itself and either holds the relevant NADCAP commodity accreditations in-house (larger shops with captive heat treat and etch lines) or controls NADCAP-accredited subcontractors for them. The grinding operation is run under the AS9100 system; the metallurgical-integrity steps around it are run under NADCAP.
The buyer's job is to confirm the full stack lines up: AS9100 current in the registrar's directory, NADCAP commodities current in eAuditNet for the specific facilities, and the prime's approved-process-source list (where one exists) covering this supplier for these processes. Missing any layer leaves a real exposure on flight hardware.
Frequently Asked Questions
Not in the way most buyers expect. NADCAP accredits special processes, heat treatment, chemical processing, plating, nondestructive testing, welding, and so on, against industry audit criteria. Conventional grinding is generally treated as a machining operation and is controlled by the shop's AS9100 quality system and the part drawing, not by a standalone NADCAP grinding checklist. What NADCAP actually accredits around a ground aerospace part is the cluster of special processes that determine its metallurgical integrity: the pre-grind heat treatment, the post-grind chemical processing and plating, the NDT, and most importantly the etch inspection used to detect grinding burn. So when a prime says a ground part requires NADCAP, they mean those special processes must be performed by NADCAP-accredited sources, not that the abrasive operation itself carries a NADCAP certificate. The correct sourcing question is which special processes touch your ground part and whether each is NADCAP-accredited and current, rather than searching for a single 'NADCAP grinding' credential that does not exist as such.
Because grinding burn is a hidden, fatigue-killing defect and detecting it reliably is itself a controlled special process. When hardened steel is ground too aggressively, with a glazed wheel, excessive infeed, or poor coolant, surface heating can re-temper or re-harden the material, leaving residual tensile stress and microcracks that can drastically reduce the fatigue life of a rotating component such as a turbine shaft or bearing journal, often with no visible sign. The standard way to find it is a controlled chemical etch (nital or temper etch, per specifications like AMS 2649) that reveals localized hardness changes as discoloration, and because that involves tightly controlled acid and alkaline baths plus trained interpretation, it falls under NADCAP's chemical processing and surface-treatment audit scope. Alternatives like Barkhausen noise analysis and X-ray diffraction for residual stress are also run under accredited control. This is why aerospace ground parts route through a NADCAP-accredited etch source after grinding; without it, a dimensionally perfect grind could still be metallurgically damaged with no proof.
Use eAuditNet, the Performance Review Institute's public system, to look up the supplier by company and location and confirm the specific special-process commodities your part needs (heat treat, chemical processing for the burn etch, NDT, plating) are listed as accredited and current. Accreditations are time-limited with merit-based intervals, so check the dates and confirm none are suspended. Verify the accreditation belongs to the exact facility performing the work, not a sister plant, and that its scope covers the specification your drawing calls out (for example, the AMS spec for the etch or the heat-treat process), since a corporate listing does not automatically cover every site or process variant. The most reliable approach is to map your ground part's full routing, pre-grind heat treat, the grind, post-grind burn etch, NDT, final finishing, and confirm each special-process step traces to a current NADCAP accreditation, whether in-house or at a controlled subcontractor. That routing map, plus a current AS9100 certificate for the quality system, is what actually proves compliance, not any single certificate.
For safety-critical aerospace grinding, almost always yes, they cover different things. AS9100 certifies the supplier's overall quality management system and includes the requirement to validate and control special processes, but it is a system-level certification. NADCAP is the third-party, industry-managed accreditation that satisfies that requirement for the specific special processes the primes care about, giving the AS9100 special-process control real enforcement. A typical prime flowdown requires AS9100 at the system level and NADCAP for the named special processes around the grind (heat treat, chemical processing/etch, NDT, plating). A grinding supplier therefore usually holds AS9100 itself and either holds the relevant NADCAP commodities in-house or controls NADCAP-accredited subcontractors. To source correctly, confirm the AS9100 certificate is current in the registrar's directory, the required NADCAP commodities are current in eAuditNet for the specific facilities, and, where one exists, the prime's approved-process-source list covers this supplier. Missing either layer leaves a genuine compliance exposure on flight hardware.
Last updated: July 2026
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