APC Ferrules Angled Surfaces Oriented in a Specific Location Relative to the Connector Key

Published: February 19, 2019

, Last updated: September 18, 2025

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With APC ferrules, we have an angled surface that MUST be oriented in a specific location relative to the connector key (if not, then two angled connectors would never mate together when connected). Any rotational deviation from this angle-to-key orientation is known as Key Error. The causes of Key Error can be difficult to identify.

Key Error is most commonly the result of the polishing fixture key width being significantly larger than the connector key width. It can also be the result of poor-quality connector components (usually plastic housings) which do not hold the ferrule solidly in the proper orientation relative to the connector’s key.

READ THE BLOG: Polished Connector Geometries, APC

Additional resources from the FOC team include:

Category Resource:
- FOC Interconnect Page
- FOC Polish Page
View the Glossary, Acronyms, Military Specifications for Connectors
Q&A Resource: email technical questions to AskFOC@focenter.com

Have questions about this FOC Tip?

Contact FOC with questions at: (800) 473-4237 / 508-992-6464 or email: FiberOpticCenter@focenter.com and we will respond ASAP.

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