Abstract: An electrical connector assembly has a threaded part having a conductor, an unthreaded part having a conductor, fittable along an axis with the threaded part for engagement of the conductors with each other, and formed with front and back axially spaced stops, and an internally threaded nut axially displaceable on the unthreaded part between the stops through a predetermined axial distance, rotatable about the axis on the unthreaded part, and threadedly engageable with the threaded part to lock the parts axially together with the nut engaging the front stop. The nut is formed with at least one axially extending and radially projecting tooth, the unthreaded part is formed with at least one axially extending and radially projecting tooth, and the teeth are so positioned that they come into engagement with each other only during a small fraction of the displacement of the nut on the unthreaded part immediately prior to engagement with the front stop.