CSA C22.2-No.40:2017 pdf download.Junction and pull boxes
4.1.2.1 Cast-metal enclosures shall be of a thickness not less than that specified in Table 1. At holes threaded for conduit, the metal thickness of the enclosure shall be not less than 3 times the pitch of thread for the conduit, with a minimum thickness of 6.35 mm.
4.1.2.2 Sheet-metal enclosures shall be of a thickness not less than that specified in Table 2 except that the thickness of metal for transformer or meter boxes may be that for the next smaller size of enclosure provided that the minimum thickness is not less than 1.34 mm. (See Clause 5.2.)
4.1.3 Reinforcement
Enclosures made of sheet steel having a thickness of 1.69 mm or less, stainless steel having a thickness of 1.34 mm or less, or sheet aluminum having a thickness of 2.33 mm or less shall be provided with reinforcement for the unsupported edge of any wall exceeding 762 mm in length. If thicker metal is used, reinforcement shall be provided for walls exceeding 914 mm in length.
Note: Turning the edge of a wall at least 90° for its full length is an acceptable means of reinforcement.
4.1.4 Rigidity
Sheet-metal boxes shall have rigidity sufficient to retain their intended shape, when mounted as if in service, so that doors and covers will fit closely. Where covers or doors are flanged they shall telescope snugly with the walls of the boxes.
4.1.6 Seams
Seams at corners and back edges, and splices in sheets shall be flanged or lapped over unless made with a continuous weld. Seams may be buttjointed, provided that they are reinforced by angle or flat strips.
Note: The bottom edge of a corner flange may be cut away at an angle to facilitate forming.
4.1.7 One-piece boxes
4.1.7.1 In a box formed of a single piece of sheet metal, the seam at the corner shall be reinforced by flanges formed of the sheet of which the boxes are made. Flanges shall be approximately as long as seams and, except where it is necessary to notch flanges for knockouts, shall have an overlap of not less than 12.7 mm.
4.1.7.2 Where it is necessary to notch flanges to accommodate conduit bushings, the notches shall be substantially circular in shape. The minimum flange width at such notches shall be not less than 3.17 mm measured on the inside of the enclosure. Adjacent notches shall not overlap such that they reduce the flange width between them to less than the required 12.7 mm.
4.1.7.3 Where rivets are used there shall be at least one rivet at each corner, located not more than 38.1 mm from the front edge of the box. For boxes from 101 to 152 mm deep, an additional rivet shall be used,while for boxes more than 152 mm deep, an additional rivet shall be used for each 76 mm, or fraction thereof in excess of 152 mm. Rivets shall be approximately evenly spaced.CSA C22.2-No.40 pdf download.