Markings on Fasteners: What Do They Mean?

Markings on Fasteners: What Do They Mean?

Contents

Manufacturer Head Markings

All fasteners come with specific markings on their heads that assist in identifying their origin, material, and size. Fastener manufacturers are responsible for ensuring clear identification of their products for customers. This guide provides useful information to help you understand and interpret the markings present on fasteners.

Manufacturer Head Markings

Every fastener manufactured by a company is required to bear a unique identifier on its head. This may simply consist of the company's initials or name. This practice was made mandatory by the Faster Quality Act to instill confidence in buyers that they are purchasing from a trusted manufacturer.

Fastener Standards

International collaboration among companies has led to the establishment of standardized markings for fasteners. These standards cover material composition, dimensions, dimensional tolerance, and coatings, providing comprehensive information about each fastener.

The American Society for Mechanical Engineers (ASME) offers the ASME B1.1 document, which outlines requirements for unified inch screw threads. ASME is widely adopted as a standard by numerous companies.

Other standards define fastener grades based on material and physical properties. For instance, SAE J429 defines the requirements for Grade 2, Grade 5, and Grade 8 fasteners. Knowing a fastener's grade provides information about its material, hardness range, electromechanical properties, and whether it adheres to the inch or metric standard.

Examples of SAE J429 Grade 2, Grade 5 and Grade 8

The Society of Automotive Engineers (SAE) has established the SAE J429 standard for Mechanical and Material Requirements for Mechanical Fasteners. This standard dictates mechanical and material properties for inch bolts, screws, studs, sems, and U-bolts, covering dimensions up to 1-½” in diameter. The increase in the fastener's grade indicates a higher tensile strength, often denoted by radial lines across the head of the fastener.

Note that Grade 2 of SAE J429 may lack markings. Also, manufacturer markings might be adjusted on the fastener's head to accommodate the representation of its grade.