John S. :A 360 degree limit appeared in the Aug. 31, 1897 Rules of the Underwriters Association of the Middle Department, which predated the National Electrical Code. No record that I know of as to how they arrived at the four ninety limit. If anybody knows, I wouldl be interested. Creighton.
#151886 - 05/16/0301:12 PMRe: Conduit Bending in 1928
Creighton, When I came into the trade....... uh, musta been 3-4 years ago the old geezers used to slap me up side the head for asking that question.
Sidewall bearing pressure aside, the "instruction" I received was that it had nothing to do with how hard we had to pull, it had to do with manufacturing a coil, and what that would do to our systems. I think it's probably a bit of both nowadays, but both do have their valid arguments.