Abstract: A welding head for projection welding wherein the spring which biases the electrode is initially preloaded to exert a significant biasing force on the electrode to maintain it against a stop to define the normal fully extended position of the electrode. The spring of the welding head is also initially precalibrated to exert an accurate predetermined biasing force on the electrode when the electrode is depressed inwardly so as to effect compression of the spring by a predetermined distance, which latter distance is of very small magnitude. The welding head is disposed in engagement with overlapping sheets so that the electrode is engaged with the sheets in alignment with a projection thereon, and the electrode is depressed through said predetermined distance so that a uniform predetermined biasing force is applied to the electrode and hence to the projection weld area.