Abstract: A method for making insulators, comprising the steps of forming a bar from a fiber glass mass impregnated with a thermosetting resin, carrying out the complete polymerization or curing substantially for the major portion of the bar length and maintaining at least one end thereof cooled at a lower temperature than the complete polymerization or curing temperature for said resin. The bar so formed is inserted in an insulating covering and a terminal fitting is applied to said uncured end of the bar, widening the fiber glasses of the uncured end of the bar against a divergent or flared surface of the terminal, and a successive step of complete polymerization or curing is carried out for said bar.