Consumer distribution boards and industrial enclosures require clean, burr-free holes for grommets, cable glands, and MCB knockouts. Thin steel panels (up to 2 mm): Bi-metal M42 hole saw. Edit: Link to datasheet of cable gland:. Running electrical wiring often requires penetrating wooden framing members, such as floor or ceiling joists, during renovations or electrical updates. While drilling is standard practice, it must be approached cautiously, as it compromises a structural member's strength. more. Drilling holes for these wires is a crucial step that directly impacts the overall performance and longevity of the electrical system. The National Electrical Code (NEC) and local building regulations set specific guidelines for hole placement, size, and spacing to prevent weakening. This guide aims to shed light on the best practices for drilling holes for electrical wiring, ensuring both safety and visual appeal.