What is the optimal hole size for cable tray bends

For most metallic cable tray bends, a hole diameter of 7–10 mm is commonly recommended, depending on tray width and fastener type.Recommended Hole SizesWhen fabricating or installing cable tray bends, the hole size should accommodate the bolts or screws used for connectors and joint plates. For example:Tray rails and bases: Drill holes with a diameter of ≥7 mm for standard fasteners on smaller trays (up to 300 mm width) to ensure secure attachment without weakening the tray structure .Larger trays (≥400 mm width): Use 10 mm holes for joint plates and connectors to prevent transverse bending under load .Coupler plates and accessories: Standard practice often uses 8 mm diameter bolts with corresponding holes for 2–3 fasteners per joint, depending on tray height and width .Considerations for Cable Tray BendsField bends: While NEC 392.18(A) allows field bending, it is generally recommended to cut and bolt straight sections rather than force a curve, especially for metallic ladder trays .Bend radius: Pre-fabricated bends are available in various radii (e.g., 12”, 24”, 36”, 48” for a 6” tray). The hole size should allow for secure bolting without interfering with the bend radius .Cable protection: Ensure that edges around drilled holes are smooth or fitted with edge protection strips to prevent cable damage during installation .Practical TipsAlways match hole size to the fastener being used (bolt diameter plus clearance).For solid bottom trays, consider additional weep holes (1/4”) for moisture drainage, but these are separate from mounting holes .Verify manufacturer specifications, as some cable tray systems may have pre-punched holes optimized for structural strength and ease of installation . By following these guidelines, you can ensure that cable tray bends are secure, structurally sound, and safe for cable installation, while maintaining flexibility for field adjustments.