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Table 6.1
Minimum acceptable thicknesses of enclosure metal
At small, flat, unreinforced
surfaces and at surfaces of
a shape or size to ensure
adequate mechanical
strength,
At surfaces to which a
wiring system is to be
connected in the field,
At relatively large
unreinforced flat surfaces,
Metal Inch (mm) Inch (mm) Inch (mm)
Die-cast metal 3/64 (1.2) – 5/64 (2.0)
Cast malleable iron 1/16 (1.6) – 3/32 (2.4)
Other cast metal 3/32 (2.4) – 1/8 (3.2)
Uncoated sheet steel 0.026 (0.66) 0.032 (0.81) 0.026 (0.66)
Galvanized sheet steel 0.029 (0.74) 0.034 (0.86) 0.029 (0.74)
Nonferrous sheet metal other than
copper
0.036 (0.91) 0.045 (1.14) 0.036 (0.91)
Sheet copper 0.033 (0.84) 0.043 (1.09) 0.033 (0.84)
6.4 A polymeric enclosure or polymeric part of an enclosure shall comply with the requirements in the
Standard for Polymeric Materials – Use in Electrical Equipment Evaluations, UL 746C.
Exception: A polymeric enclosure or polymeric part of an enclosure in accordance with 6.6 need not
comply with this requirement.
6.4 effective April 13, 1993
6.5 If the dimensional integrity of nonmetallic material employed for a part is depended upon to maintain
continuity of a grounding system, the material is to be investigated with respect to:
a) Dimensional stability;
b) Mechanical strength; and
c) Resistance to creeping and distortion at temperatures to which the material may be subjected
under conditions of intended use.
The material shall not display a loss of these properties beyond the minimum acceptable level as a result
of aging.
DECEMBER 14, 1993 UL 458 13
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