Stainless Steel Through Hole Nuts

Stainless Steel Through Hole Nuts: Features, Applications, and Maintenance

Introduction

Stainless Steel Through Hole Nuts are specialized fasteners designed for applications requiring high corrosion resistance, durability, and secure fastening. These nuts feature a threaded interior and a smooth exterior, allowing them to be inserted into pre-drilled holes and secured with a mating bolt or screw. Commonly used in industries such as construction, automotive, and marine, these nuts are valued for their mechanical properties and longevity.

Key Features of Stainless Steel Through Hole Nuts

1. Corrosion Resistance

Stainless steel through hole nuts are typically made from grade 304 or 316 stainless steel, offering exceptional resistance to rust and oxidation. Grade 316 nuts contain 2-3% molybdenum, enhancing their performance in saline or acidic environments with a pitting resistance equivalent number (PREN) of ≥25.

2. High Tensile Strength

These nuts exhibit a tensile strength of 500-700 MPa (grade 304) and up to 620-800 MPa (grade 316), making them suitable for high-stress applications. Their yield strength ranges between 200-300 MPa, ensuring reliable performance under load.

3. Temperature Tolerance

Stainless steel through hole nuts can withstand temperatures from -200°C to 800°C (grade 304) and -250°C to 900°C (grade 316), making them ideal for extreme environments.

4. Thread Precision

Manufactured to ISO 4032 or DIN 934 standards, these nuts feature metric (M3-M24) or imperial (1/4"-1") threads with a tolerance class of 6H, ensuring compatibility with standard bolts.

5. Surface Finish

Available in finishes such as plain, passivated, or electropolished, these nuts achieve a surface roughness (Ra) of ≤0.8 μm, reducing friction during installation.

Applications

1. Marine and Offshore

Used in shipbuilding and offshore platforms due to their saltwater resistance and compliance with ASTM A193/A320 standards.

2. Chemical Processing

Ideal for reactors and piping systems where chemical corrosion resistance is critical.

3. Automotive

Employed in exhaust systems and chassis components, withstanding vibrations up to 5-50 Hz and thermal cycling.

4. Construction

Used in structural frameworks, offering load capacities of 10-50 kN depending on size.

5. Food and Pharmaceutical

Electropolished nuts meet FDA and EHEDG standards for hygiene-critical environments.

Maintenance Guidelines

1. Cleaning

Use pH-neutral cleaners and soft brushes to remove debris. Avoid chloride-based solutions to prevent stress corrosion cracking.

2. Lubrication

Apply anti-seize compounds (e.g., nickel-based) with a viscosity of 150-220 cSt to prevent galling, especially in high-torque applications (>30 Nm).

3. Inspection

Check for:
- Thread wear (≥10% thread engagement loss)
- Cracks using dye penetrant testing
- Corrosion pits deeper than 0.1 mm

4. Storage

Store in low-humidity (<40% rh="">environments with desiccants. Separate by grade to avoid galvanic corrosion.

5. Re-torquing

For critical applications, re-torque after 24-48 hours of initial installation to compensate for material settling. Use a calibrated torque wrench with ±3% accuracy.

Technical Specifications Table

Installation Best Practices

1. Drill holes with HSS drill bits at 0.1-0.2 mm oversize

2. Use thread-cutting bolts for blind holes (tap drill size = major diameter - pitch)

3. Apply installation torque (T) calculated by: T = K × D × F
        Where:
        K = friction coefficient (0.2 for lubricated)
        D = nominal diameter (mm)
        F = axial force (N)

Failure Modes and Mitigation

• Stress corrosion cracking: Avoid environments with >50 ppm chlorides

• Galling: Limit installation speed to<300 rpm="">

• Fatigue: Design for safety factors ≥2.5 in cyclic loading