designed and constructed to permit conductors to be drawn in and withdrawn without physical damage.

410.77 Nonmetallic Luminaires. When luminaire wiring compartments are constructed from combustible mate- rial, armored or lead-covered conductors with suitable fittings shall be used or the wiring compartment shall be lined with metal.

410.78 Mechanical Strength.

(A) Tubing for Arms. Tubing used for arms and stems where provided with cut threads shall not be less than

1.02 mm (0.040 in.) in thickness and, where provided with rolled (pressed) threads, shall not be less than 0.64 mm (0.025 in.) in thickness. Arms and other parts shall be fastened to prevent turning.

(B) Metal Canopies. Metal canopies supporting lamphold-ers, shades, and so forth exceeding 4 kg (8

lb), or incorporating attachment-plug receptacles, shall not be less than 0.51 mm (0.020 in.) in thickness. Other canopies shall not be less than 0.41 mm (0.016 in.) if made of steel and not less than 0.51 mm (0.020 in.) if of other metals.

(C) Canopy Switches. Pull-type canopy switches shall not be inserted in the rims of metal canopies that are less than 0.64 mm (0.025 in.) in thickness, unless the rims are reinforced by the turning of a bead or the equivalent. Pull-type canopy switches, whether mounted in the rims or elsewhere in sheet metal canopies, shall not be located more than 90 mm (3'/2 in.) from the center of the canopy. Double set screws, double canopy rings, a screw ring, or equal method shall be used where the canopy supports a pull-type switch or pendant receptacle.

The thickness requirements in the preceding paragraph shall apply to measurements made on
finished (formed) canopies.

410.79 Wiring Space. Bodies of luminaires, including portable luminaires, shall provide ample space for splices and taps and for the installation of devices, if any. Splice compartments shall be of nonabsorbent, noncombustible material.

410.82 Portable Luminaires.

(A) General. Portable luminaires shall be wired with flexible cord recognized by 400.4 and an attachment plug of the polarized or grounding type. Where used with Edison-base lampholders, the grounded conductor shall be identified and attached to the screw shell and the identified blade of the attachment plug.

(B) Portable Handlamps. In addition to the provisions of 410.82(A), portable handlamps shall comply with the following:

(1) Metal shell, paper-lined lampholders shall not be used.

(2) Handlamps shall be equipped with a handle of molded composition or other insulating material.

Handlamps shall be equipped with a substantial guard
attached to the lampholder or handle.

(4) Metallic guards shall be grounded by means of an equipment grounding conductor run with circuit conductors within the power-supply cord.

(5) Portable handlamps shall not be required to be grounded where supplied through an isolating transformer with an ungrounded secondary of not over 50 volts.

410.84 Cord Bushings. A bushing or the equivalent shall be provided where flexible cord enters the base or stem of a portable luminaire. The bushing shall be of insulating material unless a jacketed type of cord is

used.

410.85 Tests. All wiring shall be free from short circuits and ground faults as defined in