CC Critical characteristic (CC)
Critical characteristic (CC) · Inspección y ensayos · ISO 1101 + ASME Y14.5
Example in plan
How to interpret it
On the drawing, “CC: wall thickness 4.2 ±0.1 · 100% inspection” states a critical characteristic (cc) requirement.
What controls
Classification identifying a characteristic whose nonconformance can affect personal safety, regulatory compliance or an essential function of the product. It does not change the tolerance: the dimension stays the same. What changes is the control regime that comes with it, which usually includes 100% inspection or statistical control with strict rules, traceability of each part and a ban on accepting deviations without formal authorization.
How to verify
It is measured using the method set in the control plan, normally with an inspection method validated for that tolerance and with evidence recorded per part or per subgroup. A gauge capability study is commonly required before the measurement system is used, because on a critical characteristic instrument uncertainty really does decide the outcome. Traceability must make it possible, in the event of a field failure, to identify which parts shipped with which results.
Common mistakes when interpreting it
- Believing the critical mark tightens the tolerance: the tolerance is the one on the drawing; what changes is the control and traceability.
- Accepting a deviation on a critical characteristic as casually as on a normal dimension.
- Modifying a tool, program or fixture that affects a critical characteristic without revalidating.
How to get it in the workshop / if it comes out of tolerance
When you see the critical characteristic symbol, treat it as a quality stop: recording it is not optional and “I'll measure it later” is not acceptable. Any process change that affects it (tool, fixture, program, material) requires revalidation. If in doubt between meeting the schedule and securing a critical characteristic, the characteristic always wins.
A part out of tolerance on a critical characteristic is not accepted by a shop-floor concession: it is segregated and escalated. If a deviation appears, the lot must be contained and what has already been delivered must be reviewed. When the process is not capable of holding it consistently, the solution is not more inspection but changing the process or the design, with engineering involved.
Related symbols
Other symbols in Inspection and testing
Related tools
ISO fits
Calculates indicative ISO 286 tolerances for shaft and hole, H7/g6, H7/h6, H7/k6 and H7/p6 fits with clearance, transition and interference graph.
Inspection Plans
Upload a plan, extract dimensions and GD&T with AI and export your inspection guideline in PDF or CSV.
Shop trigonometry
Workshop trigonometry: right triangle, C chamfer, Z countersink, sine bar, taper and polar→X/Y for CNC operators.