Cable tray fittings typically use standard bolts such as M6, M8, or 1/4"–5/16" UNC, made from steel or stainless steel, selected based on load, environment, and tray material.

Bolt Types and Sizes

• Metric bolts: Commonly M6, M8, or M10 depending on the tray size and load requirements. M6 is often used for light-duty trays, while M8 or M10 is used for medium to heavy-duty trays .
• Imperial bolts: 1/4"–5/16" UNC bolts are frequently used in North American installations, especially for ladder and channel trays .
• Length: Bolt length should accommodate the fitting thickness plus the tray flange, typically 20–50 mm for metric bolts or 3/4"–2" for imperial bolts, ensuring proper engagement with nuts and washers.

Material and Coating

• Steel bolts: Standard carbon steel bolts are used for indoor, dry environments.
• Stainless steel bolts (304 or 316): Recommended for corrosive or outdoor environments, such as chemical plants or coastal areas .
• Galvanized bolts: Hot-dip galvanized or zinc-plated bolts are used with galvanized trays to prevent galvanic corrosion.

Nuts and Washers

• Lock nuts or hex nuts: Used to prevent loosening due to vibration.
• Flat washers: Distribute load and protect tray surfaces.
• Spring washers: Optional for high-vibration environments.

Torque and Installation Considerations

• Bolts should be tightened to the manufacturer's recommended torque to avoid deformation of the tray or fittings. For example, M6 bolts are typically torqued to 8–10 Nm, and M8 bolts to 20–25 Nm, depending on material and coating .
• Ensure that bolts are compatible with the tray material to prevent corrosion or mechanical failure. Aluminum trays require stainless steel or compatible coated bolts.

Standards and Compliance

• Cable tray fittings and their fasteners should comply with NEMA VE 2, UL 568, or equivalent local standards .
• CE marking or UL listing indicates that the bolts and fittings meet safety and mechanical performance requirements.

Summary

When selecting bolts for cable tray fittings, consider:

1. Bolt size (M6, M8, M10 or 1/4"–5/16" UNC) based on tray load.
2. Material (steel, stainless steel, or galvanized) for environmental compatibility.
3. Nuts and washers to ensure secure fastening.
4. Torque specifications to prevent damage or loosening.
5. Compliance with NEMA, UL, or manufacturer guidelines for safety and warranty purposes.

Following these specifications ensures a safe, durable, and code-compliant cable tray installation suitable for industrial, commercial, or data center applications .