CSA C22.2 NO.56-2017 Flexible metal conduit and liquid-tight flexible metal conduit.
The thickness at any point of the strip material used for the various trade sizes of liquid-tight flexible metal conduit and flexible metal conduit shall be not less than the values given in Table 1 when measured before forming.
The thickness shall be measured using a micrometer caliper having flat surfaces on both the anvil and the end of the spindle, or with a dial micrometer having an anvil and presser foot 6.3 to 6.4 mm in diameter. A force of 0.83 ± 0.03 N shall be exerted on the specimen during measurement. Such micrometers shall have graduations of 0.01 mm. Where the results of measurement are in doubt after using one of the foregoing instruments, a micrometer microscope, accurate to 0.005 mm, shall be used in a referee test.
Splices in steel or aluminum strips shall not materially increase the thickness or diameter of the finished conduit or lessen its mechanical strength.
5.2.1 Interior surface
The interior surface of the conduit shall be free from burrs and sharp edges that might cause abrasion of the coverings on conductors.
The examination of the interior surface of the conduit shall be made by looking through a short specimen of the finished conduit (first from one end and then from the other) at a suitable light source of sufficient intensity to allow the interior surface to be examined.
5.2.2 Internal diameter
The minimum internal diameter of the various trade sizes of liquid-tight flexible metal conduit and flexible metal conduit shall be as specified in Table 2 when determined by means of metal plug gauges having diameters as specified in Table 2.
5.2.3 External diameter
The maximum external diameter of flexible metal conduit shall be not larger than the values specified in Table 3 when determined with a Vernier caliper accurate to at least 0.01 mm (0.001 in) or its equivalent.CSA C22.2 NO.56 pdf download.