Abstract: The present invention relates to a nut positioning pin disposed on a lower electrode for the projection welding of a nut. The present invention increases cooling and positioning accuracy, prevents entrance of sputtering particles, and increases the detecting accuracy. The present invention comprises an electrode holder (2) of a double-tube structure having a cooling water passage, a guide ring (13) for guiding a coupling rod (7) for vertical movement, an air passage (m) for preventing the entrance of sputtering particles, a coupling block (28) and a magnetic shield, which comprises a magnetic member for preventing a magnetic detecting element from being affected by an external magnetic field. The present invention accurately guides cooling water and the coupling rod in the electrode holder and prevents sputtering particles from entering the electrode holder, and prevents a detector from being adversely influenced by an external magnetic field for increased detecting accuracy.

Abstract: Welding contact tip having a wire passage for a welding wire in a center thereof, comprising a tip body and a tip end which are detachable from each other by screw-in type or taper force-in type structure, the tip body being composed of brass, aluminum, chromate copper, zirconium copper, zirconium chromate copper or phosphor bronze, the tip end being composed of copper, chromate copper, zirconium chromate copper, zirconium copper, silver tungsten, copper tungsten, alumina dispersed copper, beryllium copper or nickel beryllium copper, for prolonging a service life of the contact tip and reducing the total production cost thereof. Particularly brass is suitable for the tip body and chromate copper or zirconium chromate copper is suitable for the tip end. The wire passage in the tip body has a diameter 1.03-1.50 times a wire diameter and the wire passage in the tip end has a diameter 1.03-1.25 times the wire diameter.