ASME B18.12 (2012)

Glossary of Terms for Mechanical Fasteners

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Annotation and contents

This Standard is as summary of nomenclature and terminology currently used to define and/or describe mechanical fasteners, related characteristics, and the manufacturing processes that produce these products.  Utilization of these terms by manufacturers and consumers is intended to reduce or eliminate confusion and serve as a sound basis for communication.

ASME B18.12 provides producers, resellers, and users of fasteners and related products with definitions for:


• Basic Fastener Terminology
• Fastener Characteristics
• Fastener Head Styles
• Dimensional Terms & Size
• Terms Relating to the Manufacture of Fasteners
• Fastener Performance Terminology
• Terms Relating to the Material and Heat Treatment of Fasteners
• Coatings & Finish Terminology
• Quality Assurance Including Inspection Terminology
• Packaging

It also provides clearly defined identification of fastener product families grouped by product type (such as internally or externally threaded fasteners) to fully understand differences between fasteners such as screws and bolts. 

In the development of ASME B18.12, a number of terms were written based upon language found in more than 230 standards and other publications of ASTM, ASME, IFI, and SAE.

This Standard has assisted me in helping my customers understand how to properly identify their fasteners and accurately specify parts on their purchase orders to avoid confusion and prevent the delivery of the wrong item.
–  Chris B Williamson, Director of Quality
 Fastenal Company

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