Obtaining Nadcap Accreditation: Helping You Pass Your Audit
By Nathan Durham, Engineered Components Group Manager
Heat treatment touches everyone’s lives in one form or another. From the tools and devices we use, to the cars we drive and the planes we fly, heat treatment plays a role in creating all of these. As such, the quality and safety of these products is of the utmost importance to both the companies that make them and the consumers that use them.
The Nadcap accreditation process and Aerospace Material Specification (AMS) standards play a key role in ensuring those utilizing special processes and heat treating parts for the Aerospace industry adhere to consistent, high-quality standards. Focusing on maintaining global quality standards not only helps ensure the safety of all who use these products, but also helps you continually improve and refine your heat-treatment processes to provide your customers with the best product quality possible.
While many of our customers have found each Nadcap audit to be a unique process (depending on their specific Prime specifications, processes, equipment and more), the process of receiving Nadcap accreditation typically involves:
- Requesting and scheduling an official audit
- Performing an internal audit
- Implementing corrective actions for any findings from the internal audit
- Undergoing an official audit
- Reviewing and responding to any nonconformance findings
- Applying corrective actions to resolve the remaining issues
- Receiving Nadcap accreditation
To assist with this process, we gathered recommendations for best practices from those who have previously undergone Nadcap accreditation. Whether you are participating in an audit for the first time, or going through the reaccreditation process, our goal is to share our knowledge so you can have a quality audit experience, in addition to a quality product.
II. How to Prepare for a Nadcap Audit
While the Nadcap audit process is lengthy and complex, we have found that those who adequately prepare are able to make it through the process without difficulty. Oftentimes, the biggest step is to know where to start.
Locating Key Documents and Specifications
When preparing for a quality audit, a recommended first step is to know which documents to reference and which specifications to adhere to throughout the audit. The first place those who have gone through Nadcap accreditation say you should start is www.eAuditNet.com.
This site is offered through the Performance Review Institute (PRI), an organization that facilitates industry-managed programs and administers special process accreditation programs, such as Nadcap. PRI provides access on eAuditNet to a range of supplemental materials that can be referenced during the Nadcap audit. This website also provides procedure documents on pre-and post-audit processes, which include specific information on response timeframes, how to decrease the frequency of audits, what to do if you fail an audit and more.
Some materials commonly referenced during the audit process are the Heat Treating Task Group Audit Handbook and the Heat Treating Task Group Pyrometry Reference Guide. These materials provide a range of useful information, including:
- Supplier guidelines for auditing to Nadcap criteria
- General heat treatment items (e.g., testing and inspection, vacuum considerations, etc.)
Overall, the handbook and reference guide offer guidelines intended to assist you with better understanding and meeting the items listed on the audit checklist.
Audit Checklists and Customer Requirements
You can receive Nadcap accreditation for a range of applicable programs, such as Coatings, Fasteners, Heat Treating, Materials Testing Laboratories and more. If you are planning to undergo a Nadcap audit for Heat Treating, several basic audit checklists apply to all disciplines within the Heat-Treating category, including AC7102 revision J (general baseline checklist requirements), AC7102/8 (pyrometry requirements) and AC7102/S (supplemental heat treating requirements). Depending on your processes, there may be additional checklists to which you must adhere. You can find the complete list of checklists for the Heat-Treating category on eAuditNet.
If you are seeking accreditation by a specific Aerospace Prime, the supplemental checklist (AC7102/S) provides additional requirements. Primes are companies that take on the total responsibility for any given project and normally build the major elements of a product in their own plants (e.g., Boeing); however, they often subcontract to other companies for the various parts and systems needed. As such, we have found that it is extremely important to be familiar with both the common industry standards and the customer's requirements and specifications before moving forward in the audit process. Overall, these documents are extremely important to be familiar with and adhere to, as they are the standards by which you will be audited.
Consulting and Networking with Suppliers
In addition to becoming familiar with key documents and specifications, consulting and networking with other suppliers (i.e., a company that processes components used by Primes) can help you determine additional best practices for preparing for an audit. PRI holds three annual meetings and attending them is one such opportunity to discuss others' audit experiences. If you are unable to attend a PRI meeting, you can review the meeting notes, which include information on discussions and decisions made on certain issues and/or specifications. You can find the meeting notes on the eAuditNet website.
Overall, our customers have found that speaking to other quality managers about their Nadcap audit exposes them to different points of view and helps them gain a better understanding of certain specifications. As an added bonus, open discussions about best practices and recommended methods help them better regulate themselves and ensure they consistently adhere to a global quality standard.
Scheduling the Nadcap Audit
Once you have reviewed and understand the applicable checklists, reference materials and customer requirements, and are fully prepared to perform an internal audit, it is time to schedule the official Nadcap audit through the eAuditNet website. When doing so, it is important to know these answers:
- During the audit, will you be running real orders for an Aerospace customer or sample parts?
If you will be using sample Aerospace parts, it is recommended that you inform PRI in advance.
- Have you defined the scope of accreditation for which you want to be audited?
It is important to know the processes and specifications beforehand as you will be required to define the scope when scheduling the audit, as well as verify it at the beginning of the official audit.
- Do you already have an acceptable quality system approved?
If you do not have acceptable quality system approval (e.g., AS/EN/JISQ 9100 and AS/EN 9110, ISO/IEC 17025), a standard audit process includes AC7004 (Aerospace Quality Systems) being added to your scope of accreditation. If that occurs, the Nadcap auditors will include a one-day Quality System audit as part of the official audit process to verify that you adhere to this specification.
If you already have acceptable quality system approval, you must provide evidence of it when scheduling, or at the start of, the official audit. If you are unable to provide documentation, the auditor will perform the Quality System audit.
- Have you scheduled enough time to prepare for and perform an internal audit?
The Nadcap accreditation process requires you to perform an internal audit – a form of self-assessment that is used to measure your strengths and weaknesses against the Nadcap audit requirements  – and submit the results at least 30 days prior to the official audit. However, it is recommended that you actually perform the internal audit anywhere from three to six months before the official Nadcap audit. We have found that making sure you factor in enough time to not only prepare for and perform the internal audit, but to also work out any issues you might encounter, can help the official audit process go more smoothly.
These are a few examples of things to consider both before and while scheduling your official audit. While just one initial step on the road to accreditation, our discussions with those who have gone through the process indicate that the more prepared you are from the very beginning, the more successful you will be later on in the process.
III. Understanding the Internal Audit Process
A critical part of preparing for the official Nadcap audit is making sure you understand exactly what will be required for the internal audit. Internal audits involve performing quality system audits (e.g., AS9001 or AC7004) and live job audits, as well as reviewing past surveys, system accuracy tests, leak tests, maintenance logs and historical jobs. During the internal audit, it is recommended that you utilize the audit checklists – which can be found on eAuditNet – to ensure you are adhering to key specifications, as well as help you identify any potential findings.
Prior to submitting the internal audit results to PRI as proof of completion, some recommend performing one or more internal audits to become more familiar with the process, as well as to work through any corrective actions you may need to implement. Another potential approach is to hire an outside consultant to perform the internal audit for you; this helps provide a more realistic perspective of what might occur during the official audit.
Throughout the internal audit, it is generally advised that you record where in the system you meet requirements, as well as record where you have objective evidence of compliance. Examples of objective evidence could be notes that refer the auditor to a specific section in the Quality Manual, reference training files in the Production Manager's office and/or state the auditor should see the Sales Manager for customer satisfaction surveys.
During an internal audit, it is required to conduct live job audits (with either real or sample Aerospace parts) as this can make it easier to identify any potential nonconformances that the auditor might find during the official Nadcap audit. It is also helpful to review a balance of live and historical job audits; most recommend performing a minimum of 10 job audits with at least two job audits for each Prime. However, regardless of which audits you perform or prepare, it is essential to make sure all your records are in order for the official audit as the auditor could ask to see anything – from paperwork for a job that occurred three months ago to TUS results for initial surveys from several years ago.
Preparing for Job Audits
When it comes to performing job audits during the internal and official audit, there are a few recommended best practices that we have found help contribute to a straightforward audit process:
Do You Know the Instrumentation Type?
As part of the job audit, some have found that auditors will typically verify you are meeting all the requirements of AMS 2750. As such, it is essential that you have records on hand that clearly demonstrate how you are meeting all of the necessary requirements. In combination with meeting all the requirements for AMS 2750, it is also required that you define your instrumentation classes and types, work zones, etc., as well as have the proper documentation available to show the auditor. During the internal audit, then, it is recommended that you carefully review this information when performing job audits to ensure everything is in order for the official audit.
Do You Know the Soak Requirements?
During the job audit, the auditor will also typically review the cycle data to make sure the cycle complies with the customer's requirements for the beginning and end of the soaking time (i.e., combination of first-in or last-in and first-out or last-out). As such, you should also carefully review your own cycle data during the internal audit process.
We have found that an important step is verifying your customer's initial soak requirements prior to running a cycle and listing this information on the process sheet in the job traveler. If you are unsure about the requirements for the start and end times, it is recommended that you refer to the guaranteed soak-in table, which can be found on eAuditNet in Section 12.4.3 of AC7102, or to other industry and customer specifications that call out this information.
Do You Understand Flowdown Procedures?
When reviewing production cycles during job audits – whether it is for the internal or official audit – we have found that it is important to understand how flowdown procedures work.
To start, it is recommended that you have all material testing parameters listed on the PO and internal documents, such as the job traveler. In addition, if your material testing is outsourced, then you should provide these specifications to the calibration service provider and have them document the specifications on their test reports.
Another aspect of flowdown procedures we have found to be required is knowing the Prime and/or end user of the part. For example, a supplier could run over four hundred production orders in one day; however, they are required to know the Prime (i.e., find out if any of the components will be used for a specific Aerospace Prime and which one).
However, knowing how to perform job audits correctly – from verifying the instrumentation type to understanding flowdown procedures – is just one aspect of performing an internal audit. It is also essential to review commonly experienced nonconformances as part of your internal audit process. Doing so should assist you with identifying any nonconformances for which you need to perform root-cause analysis and apply corrective action before the scheduled official Nadcap audit.
Reviewing Common Nonconformances
Another valuable step is reviewing PRI's list of common nonconformances before you begin your internal audit and confirming you are in compliance as you go through your internal audit. This list is created by PRI every year and highlights the most common nonconformance reports (NCR) written during the previous year.
You can find these lists, as well as other NCR-related materials (e.g., ineffective NCR responses), on eAuditNet. By reviewing these lists before starting your internal audit, you are better able to determine the extent to which you might need to make adjustments, implement additional training, etc. before the official audit occurs.
Two common nonconformances frequently occurring from year-to-year include:
- Not having a documented procedure in place, or not correctly following documented procedures
- Not providing intervals for retraining and evaluations
Overall, by familiarizing yourself with common nonconformances, you can better avoid them during your own accreditation process, as well as refine and improve other aspects of your heat-treatment processes. We will examine some best practices for avoiding these nonconformances – from knowing which specifications to note to defining retraining intervals.
Incorporating Documented Procedures
Making sure you correctly document procedures and know exactly what needs to be done is one example of when reviewing the audit checklists during the internal audit can help. One of the many questions asked on the audit checklists touches upon this very subject:
"Does the supplier have an internal procedure, or procedures for Pyrometry addressing all the aspects of AMS 2750F and other customer specifications applicable to their operations?" .
Essentially, this question is asking if you have procedures set in place that, first, state what you do to fully comply with AMS 2750F, and second, incorporate any additional Prime specifications to which you are required to adhere.
Occasionally, this requirement leads to a nonconformance as some suppliers might forget to note any additional applicable Prime specifications – which can be found in AC7102/S. We have learned that it is also essential to know which specifications take precedent over others (i.e., Prime or AMS 2750F specification) so that, when it comes time for the official audit, you can ensure you are adhering to the strictest applicable requirements.
If there are no documented procedures in place, this can also result in a nonconformance. Additionally, if it is not documented how System Accuracy Tests (SAT) or Temperature Uniformity Surveys (TUS) are performed as part of the procedures followed to comply with AMS 2750F, this can also lead to a nonconformance.
Discussing this issue with our customers, we have also found that that some suppliers will only present the auditor with the SAT and TUS reports submitted by their calibration service provider. However, it is required that you also submit the internal procedure's form number on the SAT and TUS reports, as well as have the calibration service provider's procedures on hand. In the end, this common nonconformance illustrates the importance of preparing for the audit process and going through each relevant audit checklist to make sure you fully understand and adhere to each listed requirement.
Implementing Training and Retraining Intervals
Another common nonconformance involves advancing employees' general knowledge of the processes ran within their equipment, as well as having a procedure in place for training, retraining and periodic evaluations of employees. The exact checklist question asks:
"Do records indicate that training is scheduled and attended in accordance with procedures and documented ... Do records indicate that the evaluations are performed at documented frequencies and the results reviewed with employees in a program of continuous improvement of personnel?" .
When reviewing this question during a typical official audit, the auditor will not only want to confirm that procedures for training, retraining and evaluations are in place, but they will also want to verify that these procedures will state the rate at which retraining and evaluations will occur.
From our experience with those trying to receive Nadcap accreditation, we have found that not having documentation of these events is equivalent to not having a procedure in place – which will result in a nonconformance. As a result, it is important when creating procedures for training, retraining and evaluations to not only include intervals for retraining and retesting employees, but to also define these intervals and provide documentation.
In the end, these are just two examples of common nonconformances, which can result from a range of oversights, from non-certified overtemperature thermocouples to not documenting the uniformity tolerance at each surveyed temperature. This is why it is imperative that you plan to evaluate every item referenced on the applicable Nadcap audit checklists, AMS specifications and PRI's list of common nonconformances prior to the official audit.
Finishing the Internal Audit
Once you have concluded the internal audit, it is important to follow the proper steps outlined by PRI in preparation for the official audit. These steps include:
- Reviewing any findings (i.e., nonconformances)
- Performing root-cause analysis
- Implementing corrective actions
To start, a finding is essentially a nonconformance that you identify during the internal audit (or the auditor identifies during the official audit).
Nonconformances can fall into one of two categories: major or minor. A minor nonconformance is "any single system failure or lapse in conformance with the applicable standard or audit criteria" . A major nonconformance is either "the absence of, or systemic breakdown of, the process control and/or quality management system," or "any nonconformance where the effect impacts or has the potential to impact the integrity of the product" . In other words, a minor nonconformance is any small deviation from Nadcap/AMS specifications or customer standards that does not impact the product (e.g., a typographical error); whereas, a major nonconformance can mean there is a lack of control over the process or product quality, or that the safety of the product is significantly compromised. However, if a minor nonconformance could affect the product (e.g., not having a thermocouple calibration document on hand), then it becomes a major nonconformance.
While reviewing your findings after the internal audit, you should prioritize and group any related findings together. Once you have established the order in which the findings should be addressed, the next step is to determine the root cause of each nonconformance. If you have identified a variety of findings, we find that starting with the most drastic findings (e.g., any major nonconformances) is typically the recommended approach so you can immediately ensure the basic safety and quality of your products.
Performing Root-Cause Analysis
When determining a root cause (i.e., the reason why a nonconformance occurred), you will need to define the "5-Whys," as noted by PRI . Doing so will help identify the chronological events that led to the ultimate root cause. If any of the answers to the "why" questions are "as a result of" or "because," then the true root cause has not yet been identified and further investigation is required.
A common misconception concerning appropriate root causes is that you can list the immediate contributing factors or simply list human error (e.g., the operator did not adhere to the correct processes when positioning the load thermocouples in the furnace). However, the root cause was not human error; rather, a more acceptable root cause might be: a procedure was not in place to provide the operator with appropriate training and retraining at regular intervals.
Let's take a closer look at how to determine the root cause of an issue. For example, if the problem is that you were late to work, you might ask yourself, "Why was I late?" If the answer is "the car wouldn't start," then this is a contributing cause and you have not yet identified the true root cause. As a result, you must continue to ask yourself why questions (e.g., "why didn't the car start") until the answers are no longer "as a result of" or "because" and you discover the true root cause, such as "the battery was old." In the end, you know the true root cause has been found when continuing to ask why no longer adds value, meaning any further possible answers would not help prevent a recurrence, reduce erratic results or provide cost savings .
Applying Corrective Actions
Once you have determined the root-causes for all of the findings from the internal audit, it is required that you define the corrective action made to address the issue, as well as cite timing of the implementation. Some that have gone through the audit process have mentioned that if a corrective action implemented as a result of an internal audit has not yet been fully applied due to time constraints, as long as you are working to apply corrective actions the Nadcap auditor might not write an NCR for the same finding. This, of course, depends on the exact finding, as well as the auditor's ability to verify later that the corrective action was truly implemented.
For example, during the internal audit, you identified a nonconformance in relation to a typographical error that had no product impact in the calibration report for the overtemperature controller. As a result, the root cause might be a lack of quality resources for reviewing calibration reports. However, if the calibration service provider is not available to correct the root cause within the 30 days before the scheduled audit, you should note in the internal audit report that the corrective action will be fully implemented and verified during the next calibration with the future date. After the official audit, the auditor will then verify that the corrective action was implemented by the aforementioned date. Overall, we have found that it is required to document the implementation of any corrective actions after the internal audit, as auditors will verify that these corrective actions are still in place during the official Nadcap audit.
Generally speaking, implementing corrective actions for any findings discovered during the internal audit is one of the final steps in performing an internal audit. From there, you want to ensure all of the proper documentation from the internal audit is submitted to PRI at least 30 days before the official audit.
IV. Executing a Successful Official Audit
So, now you have scheduled the official audit, performed the internal audit and submitted all of the necessary documentation. The next step in the Nadcap accreditation process is undergoing the official audit. As you prepare to start the official audit, it is important to recognize that this is an independent, objective activity designed with the purpose of verifying you are operating under a specified state of control . This is important because, by having control over your processes and equipment – essentially every aspect that goes into creating a product – you are best equipped to consistently meet and adhere to quality standards for all Aerospace products.
The reason control of your processes is so important is because certain processes, such as heat treatment and brazing, are considered special processes. In other words, special processes are those that, when performed, you cannot fully verify the final product meets the specified requirements. As such, the process must be validated in advance to ensure these products are free of defects and meet the Aerospace industry's high-quality standards. In the end, the only way to guarantee quality results is by guaranteeing the process and demonstrating control through a Nadcap audit.
However, besides preparing for the audit process and performing an internal audit, there are a few best practices recommended for executing a successful audit, including scheduling key personnel, informing the auditor of any schedule considerations in advance and verifying the desired scope of accreditation.
According to some, a key first step for ensuring a successful official audit is having the personnel who performed the internal audit available during the official audit process. Based on recommendations, key personnel typically include those with the greatest depth of knowledge about your day-to-day processes, those who regularly operate the equipment, etc. By considering who is most involved with your everyday processes and equipment, as well as those who fully understand and can explain said processes, you should be able to get a sense of the personnel you want to have available during the official audit.
It is also important that you inform all personnel of the audit process and confirm that they all understand the role they play in making the audit successful. This helps prepare them as the auditor might choose to talk with any one of them during the official audit.
Informing the Auditor of Schedule Considerations
During the official audit, scheduling is critical. In most cases, the auditor is required to be on site for four to five full days, if not longer. As such, it is required that you inform the auditor at the start of the official audit of what Primes you want to be approved for, as well as what is scheduled with production over the next few days (e.g., if there are any upcoming furnace cycles). This will help the auditor schedule their visit more efficiently. In turn, this will help you manage your production schedule and maximize productivity.
Overall, many have found that informing the auditor of the production schedule, as well as any personnel schedule considerations that should be taken into account (e.g., if a specific furnace operator only works until 2 p.m. during the week), helps the auditor plan out and balance different aspects of the official audit.
Verifying Scope of Accreditation
When starting the official audit, one of the very first things you typically do with the auditor is verifying that the scope of accreditation submitted when scheduling the audit has not changed. Essentially, whichever standards and specifications you select to be audited against are exactly what the auditor will go over in detail during the audit process. It is also important to note that you cannot remove or add any areas once the auditor has finished verifying the scope of accreditation.
The Audit Process
The official audit, as our customers typically experience it, is generally divided into two segments: the Quality System audit and the Process audit.
The Quality System audit is approximately one day in length. If you provided evidence of an acceptable quality approval when scheduling the audit, then the auditor will not perform the Quality System audit, according to PRI. If you do not have an acceptable quality approval already, the auditor will then typically perform the Quality System audit, which involves verifying that you are meeting all the requirements for a quality specification.
After the Quality segment of the audit is completed, it is time for the Process audit, which is approximately four days long. However, the Process segment could be longer, depending on the number of Primes for which you are being accredited, the scope of accreditation, etc.
Typically, during this portion of the official audit, an auditor spends a significant portion of time reviewing specification checklists and both historical and live jobs. As such, we have found that it is required to have a large number of both historical and live jobs prepared – as defined on the eAuditNet website – as auditors will ask for different historical jobs besides the initial ones prepared, as well as request to do a live job audit.
Interacting with the Auditor
Throughout the official audit process, you will interact with the auditor in a variety of ways – from discussing your understanding of specifications to reviewing any findings. As such, a key part of audit process is providing credible information and data on how the process is controlled, as well as explaining it to the auditor in a clear and concise manner.
All Nadcap auditors have been extensively trained to identify nonconformances and ensure all specifications are being adhered to within the set standards. By discussing any nonconformances you received with the auditor, you can better understand all aspects of the situation, as well as why you received it. Recommended methods for interacting with the auditor include presenting your reasons for doing things a certain way in a factual manner, as well as discussing how you interpret a certain specification to determine where any misunderstanding might have occurred.
Overall, we have found it is vital to keep a few key best practices in mind for ensuring one's interactions with the auditor are calm and professional:
Balancing the Auditor's Time
With the few days in which the auditor must review everything, as well as the amount of time each job audit can take up, it is helpful to provide a daily reminder of when loads are being run, what times certain personnel are available, etc. In addition, the auditor will divide their time between the office and the shop floor. Being prepared, regardless of when they want to review a certain area or job audit, will help avoid any delays in the audit process.
Explaining Interpretation of a Specification
When interacting with the auditor, there may be times when you will need to explain how you interpret a specification. When doing so, many recommend having collected data, documented procedures and any additional information on hand for any discussions that may occur. In addition, being able to provide an explanation for why you do things a certain way not only helps you better understand the nuances of various specifications, but it also helps you decide if any refinements need to be made in your process.
V. Finishing the Audit Process
We have found it is important to follow the proper steps – regardless of whether the audit was passed or failed. These recommended steps are nearly identical to those followed after the internal audit, but with a few key differences.
One of the first and most important steps is to review any findings with the auditor and make sure you understand each one. The reason this step is so vital is because if you do not understand what you received a finding for, you will not understand what to correct.
After the conclusion of your audit, you must then respond to all findings, making sure to include:
- The corrective action taken
- The root cause of the nonconformance
- The product impact of all nonconformances
- The action taken to prevent future reoccurrences
- The objective evidence
Performing Root-Cause Analysis
The process of performing root-cause analysis for the official audit is identical to the steps applied during the internal audit. However, a recommended best practice is to take advantage of the root-cause trainings PRI offers so as to better understand how to identify them. This is because, depending on the auditor's findings, related findings are sometimes grouped together depending on the root cause. In the end, while having a similar root cause does not necessarily mean the number of findings will be reduced, knowing how to perform root-cause analysis is an essential part of the official audit process.
Applying Corrective Actions
Once you have performed root-cause analysis, it is time to apply corrective actions. When making corrective actions, you should define the resolution made to address the issue, as well as cite timing of the implementation. For example, if there was a finding for improperly located load thermocouples and you determined the root cause was a lack of operator training, the corrective action would be to provide operator training at a specific frequency; you should then note the training schedule that has been followed since the corrective action was implemented.
When going through these processes after the audit, it is also important to note that you have 21 calendar days from the end of the official audit to submit your initial response concerning the findings. You then have seven calendar days to submit each subsequent response with four total responses allowed. Thirty extra days are allotted if more time is needed; however, utilizing these extra days can affect your merit and using more than the 30 extra days – or more than the allotted four responses – could lead to an audit failure .
As you end the Nadcap accreditation process, it has been found that keeping track of things that went smoothly, as well as areas that could use some refinement, helps contribute to your success when undergoing future audits. By continually refining your processes and methods, you are then better able to enhance the quality and safety of the components you process.
As with any quality audit, auditors are tasked with evaluating a specific set of standards and noting any findings that do not adhere to the set specifications. As such, they play a key role in ensuring suppliers successfully adhere to the high-quality standards of the Aerospace industry. After all, Primes have established global quality standards so that planes can travel safely to their destinations and so everyone can be confident that air travel is safe and secure. Ultimately, the safety of Aerospace products is of the utmost importance, and to ensure these high global standards are met, quality standards must be regularly enforced.
The Nadcap accreditation process not only helps ensure the safety of all who utilize these products, but it also helps you continually refine and improve your processes. In the end, whether this is your first or tenth Nadcap audit, continually refining and developing your audit process will contribute to a positive and successful audit experience each time.
 American Society for Quality, "What is Auditing," 2013, http://asq.org/learn-about-quality/auditing/.
 Performance Review Institute, "AC7102/8: Nadcap Audit Criteria for Heat Treating Pyrometry," 2014, pp. 1.
 Performance Review Institute, "AC7102 Rev. H: Nadcap Audit Criteria for Heat Treating," 2014, pp. 6.
 Evans, Paul and Eric Jacklin, "Nadcap Supplier Tutorial," Performance Review Institute (June 2013), pp. 28.
 Performance Review Institute, "Root Cause Corrective Action - Nadcap Style," 2014, pp. 1-11.
 Ibid., 7.
 American Society for Quality, http://asq.org/learn-about-quality/auditing/.
 Evans, pp. 37