Foundries, blacksmiths' shops, boiler shops, car shops, locomotive or railway repair shops or any metal working shops employing pneumatic or electric reciprocating hammers or chisels; power forging, riveting, hammering, punching, chipping, drawing, rolling or tumbling of iron, steel, brass or copper except as a necessary incident of manufacture of which these processes form a minor part and which are carried on, provided that the noise and vibration thereof is carried on within the walls of the building, structural steel or fabricating shop.