Finished Hex Nuts

A Guide to Finish Nuts: Grades and Plating Options

Choosing the Right Strength and Protection for Your Application

Finish nuts are essential fastening components used across mechanical, automotive, construction, and industrial applications. Designed to pair with bolts and threaded fasteners, finish nuts provide secure, load-bearing connections that maintain joint integrity under stress, vibration, and torque. Selecting the correct grade and plating option is critical to achieving the required strength, durability, and corrosion resistance for your specific environment.

Fractional Grades of Finish Nuts

Understanding Strength Levels for Inch-Series Applications

Finish nuts in fractional (inch) sizes are commonly available in Grade 2, Grade 5, and Grade 8, each offering different performance characteristics.

Grade 2 Finish Nuts
Manufactured from low-carbon steel, Grade 2 nuts are intended for light-duty, non-critical applications. They are ideal for assemblies with minimal load requirements and are commonly used in general maintenance and light fabrication.

Grade 5 Finish Nuts
Grade 5 nuts are made from medium-carbon steel and heat-treated for increased strength. They provide higher tensile and proof strength than Grade 2, making them suitable for automotive, industrial, and mechanical assemblies requiring moderate load capacity.

Grade 8 Finish Nuts
Grade 8 nuts are high-strength fasteners produced from carbon alloy steel and heat-treated to withstand extreme torque and stress. These nuts are designed for heavy-duty machinery, structural connections, and demanding industrial environments.

Metric Grades of Finish Nuts

Performance for Metric Fastening Systems

Metric finish nuts are typically classified as Grade 8.8 and Grade 10.9, reflecting their tensile strength in megapascals (MPa).

Grade 8.8 Nuts
With a tensile strength of approximately 800 MPa, Grade 8.8 nuts are widely used in automotive, machinery, and structural applications where reliable, medium-strength fastening is required.

Grade 10.9 Nuts
Offering tensile strength near 1,000 MPa, Grade 10.9 finish nuts are designed for high-stress applications such as heavy equipment, bridges, and structural assemblies.

Plating Options for Finish Nuts

Corrosion Resistance and Environmental Protection

Finish nuts are available with multiple plating options to match environmental conditions:

• Plain Finish – Bare steel; best for dry, indoor applications

• Cr3 (Trivalent Chromium) – Environmentally friendly corrosion resistance

• Cr6 (Hexavalent Chromium) – Enhanced corrosion protection for demanding environments

• Galvanized – Thick zinc coating for outdoor and marine exposure

Selecting the Right Finish Nut

Understanding finish nut grades and plating options ensures optimal performance, safety, and longevity. Whether for light-duty assemblies or high-load structural applications, choosing the correct finish nut enhances reliability and extends service life across all fastening systems.