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Critical, Major and Minor Defect Classification List

Sampling plans such as ANSI Z1.4 need defects sorted into classes, and each class often has its own AQL. This list gives a practical starting point for critical, major and minor examples that you can adapt.

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Defect	Area	Suggested class	Rationale
Crack in load bearing weld or casting	Structure	Critical	Can cause failure and injury
Missing safety guard or interlock	Assembly	Critical	Hazard to the end user
Wrong part or wrong material grade	Identification	Critical	Fit or safety function cannot be assured
Exposed live conductor	Electrical	Critical	Shock or fire risk
Missing required label or warning	Labeling	Critical	Regulatory or safety requirement
Critical dimension out of tolerance	Dimensional	Major	Fit or function affected
Missing fastener	Assembly	Major	Function or durability affected
Burr on a mating or sealing surface	Machining	Major	Leak or wear risk
Cold solder joint	Electronics	Major	Intermittent failure
Insufficient plating thickness	Finish	Major	Corrosion protection reduced
Incorrect torque or unverified torque	Assembly	Major	Joint integrity at risk
Packaging damage exposing the product	Packaging	Major	Product damage in transit
Scratch on a non functional cosmetic surface	Cosmetic	Minor	Appearance only
Slight color variation within sample range	Cosmetic	Minor	Appearance only
Burr on a non critical edge	Machining	Minor	Handling or appearance only
Minor label misalignment	Labeling	Minor	Content legible and correct
Loose threads or trim on soft goods	Textile	Minor	Appearance only
Carton dent without product damage	Packaging	Minor	No functional effect

These classes are suggestions. Your customer, drawing, workmanship standard or quality agreement defines the final classification and may treat any of these differently. Document the agreed list in the inspection procedure.

Standardise defect codes in your ERP

Optional: we can help map a defect classification list to defect codes and Pareto reports in your ERP.

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How to use the list

Search for the defect you see or the area you inspect. Treat the suggested class as a draft and agree it with your customer or supplier. Then copy the agreed rows into your inspection instruction so every inspector classifies the same way. Export the table to Excel and add a column with a photo reference or limit sample ID for borderline cases.

What the three classes mean

A critical defect is one likely to cause harm or violate a regulation. A major defect is likely to result in failure or materially reduce usability. A minor defect departs from the standard but is unlikely to affect use. Common practice is zero tolerance for critical, a tighter AQL for major, and a looser AQL for minor, but the numbers come from your contract or internal policy, not from this list.

Critical: safety, legal or regulatory impact
Major: function, fit or durability impact
Minor: appearance or small departure
Agree the class before the first inspection

Common mistakes

Leaving classification to the individual inspector produces unstable results between shifts and sites. Another mistake is calling everything major so that the AQL becomes unreachable, which leads to ignored rejections. Use limit samples and photographs, review the list after every customer complaint, and set the defect code in your ERP so Pareto reports use the same categories.

Frequently Asked Questions

Who decides whether a defect is critical, major or minor?

The customer specification, drawing or quality agreement decides. Where none exists, the manufacturer's quality procedure defines classes, ideally agreed with the customer before the first lot is inspected.

Should critical defects have an AQL?

Many organisations use zero tolerance for critical defects, meaning any occurrence is a rejection and often triggers 100 percent screening. Some contracts still state an AQL such as 0.065 for criticals. Follow your contract.

How many defect classes should I use?

Three is the common choice because it matches how sampling standards and consumer goods audits describe defects. Aerospace and automotive customers often prefer a defect code list tied to characteristics instead of classes.

Can one defect have different classes in different products?

Yes. A scratch is cosmetic on a housing but major on a sealing surface. Classify by effect on the specific part, not by the defect name alone.

If defect codes differ across plants, Netray can help standardise them and report on defects by class in your ERP.

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