Abstract: A grounded metal enclosure circuit-breaker comprises, for each pole, a metal enclosure having two insulative bushings. The enclosure and the bushings are adapted to be filled with insulative gas. The enclosure contains first and second metal supports and a set of fixed contacts and a set of mobile contacts respectively supported by the first and second metal supports. The bushings each comprise a metal conductor surrounded by an insulative covering, each of the first and second metal supports having fixed to it a metal part having an annular portion surmounted by a deformable conical portion. The metal part has an axial bore in which the bushing conductor is inserted. A ring having a conical interior surface complementary to that of the conical portion is screwed onto the annular portion.