I thought that NPT was not the thread used by rmc conduit and imc conduit systems. Please correct me if this is untrue. The gentleman states a tapered thread is required. I don't know first hand but have all ways thought that electrical threads were nearly flat and opposed to the National Pipe Thread standard which is regularly used by plumbers. We have always purchased the "other" dies, I can't recall their proper name at this time, instead of the plumbers' NPT dies.
