Appearance
Aerospace deep hole drilling is one of the most heavily regulated precision manufacturing processes. Every hole drilled in a landing gear component, engine shaft, or flight control actuator must meet not only dimensional tolerances but also strict quality system requirements under AS9100 and, for many applications, Nadcap special process accreditation. This guide covers what these certifications require, how they apply to deep hole drilling operations, and what shops need to do to achieve and maintain compliance.
Why Aerospace Certification Matters for Deep Hole Drilling
Deep hole drilling shops that serve aerospace customers must meet certification requirements that go far beyond general manufacturing quality standards. The reasons are specific to the process:
Process Risk
Deep hole drilling creates features that are often impossible to fully inspect after manufacture. The bore surface at 500 mm depth cannot be visually examined or reached with conventional inspection tools. The process itself must be proven to produce acceptable results — inspection alone cannot guarantee quality.
This is why aerospace regulators treat deep hole drilling as a special process under Nadcap: the metallurgical condition of the bore surface (freedom from burning, micro-cracking, excessive residual stress) cannot be fully verified by post-process inspection.
Regulatory Requirements
Major aerospace primes — Boeing, Airbus, GE Aerospace, Rolls-Royce, Pratt & Whitney, Safran — require their suppliers to hold AS9100 certification as a minimum condition of doing business. For specific part numbers involving deep hole drilling, Nadcap CMSP (Conventional Machining Special Process) accreditation may also be contractually required.
Liability and Traceability
Aircraft components operate under extreme conditions. A deep hole drilled with incorrect parameters can lead to fatigue failure, with catastrophic consequences. Full traceability from raw material through every machining operation is essential for liability management and regulatory compliance.
AS9100: The Aerospace Quality Management System
AS9100 is the internationally recognized quality management system standard for the aerospace industry. It is maintained by the International Aerospace Quality Group (IAQG) and is currently at Revision D (AS9100D).
Relationship to ISO 9001
AS9100 is built directly on ISO 9001 — it incorporates every ISO 9001 requirement and adds approximately 100 additional requirements specific to aerospace, defense, and aviation.
| Aspect | ISO 9001 | AS9100 |
|---|---|---|
| Scope | All industries | Aerospace, defense, aviation |
| Risk management | General risk-based thinking | Formalized risk management |
| Product safety | Not explicitly addressed | Explicit safety controls |
| Counterfeit parts | Not addressed | Strict prevention protocols |
| Configuration management | Basic | Rigorous, documented process |
| Supplier management | Standard requirements | Enhanced oversight |
| First Article Inspection | Not required | Mandatory (AS9102) |
Key AS9100 Requirements for Deep Hole Drilling Shops
Risk Management (Clause 8.1.1)
AS9100 requires formal risk analysis and mitigation strategies at every stage. For deep hole drilling, this means documented risk assessments for:
- New part programs (hole geometry, L/D ratio, material)
- Process parameter changes (speed, feed, coolant changes)
- Tooling changes (new drill designs, guide pad materials)
- Material lot changes (hardness variation, machinability differences)
Product Safety (Clause 8.1.3)
Safety-critical features of deep-drilled holes — such as bore surface integrity, straightness, and absence of cracks — must be identified and controlled throughout manufacturing. The risk assessment must consider how a failure of each feature would affect the final product.
Configuration Management (Clause 8.1.4)
Every revision to the drilling process — tool diameter change, coating change, parameter adjustment — must be tracked, documented, and communicated. This is critical for deep hole drilling where subtle process changes can affect hole quality.
Counterfeit Parts Prevention (Clause 8.1.7)
Raw materials for deep hole drilling (bar stock, tubing) must be verified as authentic. This includes chain-of-custody documentation from the mill through to the finished part.
WARNING
Counterfeit material is a growing concern in aerospace supply chains. In 2023, a major aerospace supplier discovered that a batch of titanium bar stock used for deep-drilled landing gear components had fraudulent material certifications. The incident triggered a multi-million-dollar recall and a plant-wide shutdown for traceability verification. AS9100 counterfeit prevention requirements are designed to prevent exactly this type of event.
First Article Inspection (AS9102)
AS9102 defines the standardized method for performing and documenting First Article Inspection (FAI) in aerospace manufacturing.
When FAI Is Required
| Trigger | Description |
|---|---|
| New part | First production run of a new part number |
| Design change | Engineering change affecting design characteristics |
| Process change | Change in manufacturing method, tooling, or CNC program |
| Production break | Production halt exceeding 2 years |
| Location change | Change of manufacturing facility |
| Material source change | Change in raw material supplier |
The Three FAI Forms
A complete First Article Inspection Report (FAIR) under AS9102 consists of:
| Form | Name | Content |
|---|---|---|
| Form 1 | Part Number Accountability | Basic part information, bill of materials, overall FAI conclusion |
| Form 2 | Product Accountability | Raw material certifications, special process certifications, functional testing |
| Form 3 | Characteristic Accountability | Every dimension with actual measured values and tolerances |
FAI for Deep Hole Drilled Parts
For deep hole drilling, FAI requires special attention to:
- Bore diameter at multiple depths (entry, mid-point, exit)
- Straightness measurement (often using air gauging or laser measurement)
- Surface finish (Ra, Rz) along the bore axis
- Material condition at the bore surface (no burning, micro-cracking)
- Process parameters documentation (speeds, feeds, coolant pressure, flow rate)
The person performing FAI inspection must be independent from the person who manufactured the part — the machinist cannot inspect their own work for FAI.
Nadcap: Special Process Accreditation
Nadcap (National Aerospace and Defense Contractors Accreditation Program) is administered by the Performance Review Institute (PRI) . It provides special process accreditation for manufacturing processes that cannot be fully verified by post-process inspection.
Conventional Machining Special Process (CMSP)
Deep hole drilling falls under the Conventional Machining Special Process (CMSP) audit scope within Nadcap. The governing audit checklist is the AC7126 series, covering:
| Process Category | Covered Operations |
|---|---|
| Hole making | Drilling, reaming, gun drilling, BTA drilling |
| Turning | OD and ID turning, boring |
| Milling | Face milling, contour milling |
| Grinding | Surface, cylindrical, centerless |
| Finishing | Broaching, honing, burnishing, hand benching |
Why Deep Hole Drilling Is a Special Process
Deep hole drilling is classified as a special process because:
- Heat generation at the cutting edge can cause metallurgical damage (burning, re-hardening) that is not visible on the surface
- Chip evacuation challenges create the risk of chip packing, which can cold-work or score the bore surface
- Post-process inspection limitations — the bore surface at depth cannot be directly inspected
- Residual stress from the drilling process can affect fatigue life
- Guide pad burnishing creates a surface layer condition that may differ from the bulk material
CMSP Audit Requirements
The Nadcap CMSP audit evaluates the supplier's control over:
| Requirement Area | Key Audit Points |
|---|---|
| Process parameters | Speeds, feeds, coolant pressure and flow rate must be defined and documented for each deep hole drilling operation |
| Tool control | Tool selection criteria, wear monitoring, change-out intervals, tool inspection procedures |
| Equipment qualification | Machine tool calibration verified across the full range of use (not just single-point checks) |
| Coolant management | Coolant type, concentration, filtration level, temperature, change intervals |
| Maintenance | Machine tool maintenance schedules, spindle runout checks, guide bushing condition |
| Personnel training | Operator qualifications, documented training, competency verification |
| Process monitoring | For higher-risk features, automated monitoring with alarms when parameters drift outside limits |
Common CMSP Non-Conformances
Based on industry audit data, the most frequently cited non-conformances in Nadcap CMSP audits include:
- Equipment qualification not covering the full range of operating parameters
- Calibration records incomplete or out of date
- Process parameter documentation insufficient — no defined limits for speed, feed, or coolant conditions
- Training records missing or incomplete
- Process monitoring not demonstrated where required by customer specifications
Nadcap vs. AS9100: The Difference
| Aspect | AS9100 | Nadcap |
|---|---|---|
| Scope | Quality management system | Special process accreditation |
| Audited by | Accredited certification body (DNV, BSI, etc.) | PRI task group auditors |
| Audit frequency | Annual surveillance, recertification every 3 years | Typically 6–12 months |
| Focus | System and documentation | Process and technical control |
| Applicable to | All aerospace suppliers | Suppliers of special processes |
| Deep hole drilling covered? | Yes (as part of QMS) | Yes (as CMSP, if specified) |
TIP
Not all deep hole drilling shops need Nadcap CMSP accreditation. AS9100 is the baseline requirement for aerospace work. Nadcap CMSP is required only when the customer contract specifically invokes it — typically for safety-critical components such as landing gear, flight control actuators, and engine parts. For less critical aerospace applications (interior fittings, non-structural brackets), AS9100 alone may be sufficient. Check your customer's requirements before pursuing CMSP accreditation.
Certification Process
AS9100 Certification Timeline
| Phase | Typical Duration | Activities |
|---|---|---|
| Gap analysis | 1–2 months | Assess current QMS against AS9100 requirements |
| Documentation | 2–4 months | Write/update procedures, work instructions, forms |
| Implementation | 2–4 months | Train personnel, run the QMS, collect records |
| Internal audit | 1 month | Conduct internal audit, close findings |
| Certification audit | 1–2 months | Stage 1 (documentation) + Stage 2 (implementation) |
| Total | 6–12 months | Varies by shop size and starting point |
Nadcap CMSP Preparation Timeline
| Phase | Typical Duration | Activities |
|---|---|---|
| Readiness assessment | 1–2 months | Review AC7126 checklist, identify gaps |
| Process documentation | 2–3 months | Write process specs, parameter sheets, tooling standards |
| Equipment qualification | 1–2 months | Calibrate machines across full operating range |
| Internal audit | 1 month | Conduct mock audit against AC7126 |
| Application | 1 month | Submit application, schedule audit |
| Total | 6–10 months | Assuming AS9100 is already in place |
Cost Considerations
| Certification | Typical Cost Range | Notes |
|---|---|---|
| AS9100 certification | $5,000–$15,000 | Plus internal preparation costs |
| AS9100 maintenance | $2,000–$5,000/year | Annual surveillance audits |
| Nadcap CMSP audit | $4,000–$8,000 per audit | Plus preparation and corrective action costs |
| Nadcap renewal | $4,000–$8,000 per cycle | Audits every 6–12 months |
Documentation Requirements
AS9100 Required Documents
For a deep hole drilling shop, the following AS9100 documentation is essential:
| Document Type | Examples |
|---|---|
| Quality Manual | QMS scope, processes, responsibilities |
| Procedures | Document control, non-conformance, corrective action, internal audit |
| Work Instructions | Gun drilling setup, BTA drilling setup, inspection methods |
| Forms | FAI forms (AS9102), inspection reports, calibration records |
| Records | Training, maintenance, calibration, production data |
Nadcap CMSP Required Documents
In addition to AS9100 documentation, Nadcap CMSP requires:
| Document Type | Content |
|---|---|
| Process specification | Defined parameters for each deep hole drilling operation |
| Equipment qualification | Machine capability data across full operating range |
| Tooling standards | Tool identification, inspection, change-out criteria |
| Coolant management | Coolant type, concentration, filtration, change schedule |
| Maintenance records | Machine tool preventive maintenance, spindle runout checks |
| Training records | Operator competency verification for each process |
Practical Guidance for Deep Hole Drilling Shops
Starting from No Certification
If your shop currently holds no aerospace certification:
- Start with AS9100 — It is the foundation. Do not attempt Nadcap without AS9100 in place.
- Use the gap analysis to identify where your current QMS falls short
- Focus on process documentation — Deep hole drilling parameters must be written down and consistently applied
- Invest in calibration — Machine tool calibration across the full operating range is essential
- Train operators — Ensure every deep hole drilling operator is trained and their training is documented
Moving from AS9100 to Nadcap
If your shop already has AS9100:
- Review AC7126 — The full checklist is available through PRI eAuditNet
- Deepen process documentation — Nadcap requires more granular parameter definitions than AS9100
- Verify equipment qualification — Ensure machine calibration covers your actual operating ranges
- Conduct a mock audit against the CMSP checklist before the formal audit
- Prepare for shorter audit cycles — Nadcap audits occur every 6–12 months versus annual AS9100 surveillance
Maintaining Certification
Once certified, shops must:
- Monitor process parameters continuously for deep hole drilling operations
- Document all changes — Any parameter change must be recorded and justified
- Calibrate on schedule — Never let calibration expire
- Train new personnel before they work on aerospace parts independently
- Respond to non-conformances promptly with root cause analysis and corrective action
Timeline Summary
| Year | Development |
|---|---|
| 1987 | ISO 9001 first published |
| 1998 | AS9100 first published (based on ISO 9001 with aerospace additions) |
| 2000 | Nadcap program established by PRI |
| 2010 | Nadcap CMSP Task Group formed for conventional machining |
| 2014 | AS9100 Rev C published with enhanced risk requirements |
| 2016 | AS9100 Rev D published (current revision) |
| 2023 | AS9102 Rev C published (updated FAI standard) |
| Ongoing | AC7126 checklist updated regularly by PRI task groups |
FAQ
Q: What is the difference between AS9100 and ISO 9001? AS9100 includes all ISO 9001 requirements plus approximately 100 additional requirements specific to aerospace — including formal risk management, product safety, counterfeit parts prevention, configuration management, mandatory First Article Inspection, and enhanced supplier control.
Q: Does every deep hole drilling shop need AS9100 certification? Only shops that want to supply the aerospace industry. For commercial, hydraulic, automotive, or oil and gas applications, ISO 9001 is typically sufficient. AS9100 is required by most aerospace primes and their Tier 1 suppliers.
Q: What is Nadcap CMSP accreditation? Nadcap Conventional Machining Special Process (CMSP) accreditation is a special process certification for machining operations that can cause metallurgical damage not detectable by post-process inspection. Deep hole drilling falls under CMSP when used for safety-critical aerospace components.
Q: How long does it take to get AS9100 certified? Typically 6–12 months from start to certification, depending on the shop's starting point. Shops with an existing ISO 9001 QMS can transition in 3–6 months.
Q: How long does Nadcap CMSP accreditation take? Approximately 6–10 months assuming AS9100 is already in place. The process includes readiness assessment, documentation, equipment qualification, internal audit, and the formal PRI audit.
Q: What is AS9102 and why is it important for deep hole drilling? AS9102 defines the standardized method for First Article Inspection (FAI) in aerospace. For deep-drilled parts, FAI requires verifying bore diameter at multiple depths, straightness, surface finish, and material condition — documented on Forms 1, 2, and 3.
Q: How often are Nadcap CMSP audits conducted? Nadcap audits typically occur every 6–12 months, depending on audit performance. This is more frequent than AS9100 surveillance audits (annual) or recertification (every 3 years).
Q: What are the most common Nadcap audit findings for machine shops? Equipment qualification not covering full operating range, incomplete calibration records, insufficient process parameter documentation, missing training records, and inadequate process monitoring.
Q: Can a shop have Nadcap CMSP without AS9100? Technically yes, but practically no. The Nadcap CMSP audit references AS9100 requirements, and most customers require AS9100 as a baseline. It is strongly recommended to achieve AS9100 before pursuing Nadcap.
Q: What happens if a certification lapses? The shop cannot produce parts for aerospace customers until certification is reinstated. Parts produced during the lapse period are typically non-conforming and must be documented as such. Restoration requires a full recertification audit.