electrode 16 has a tip 22 of like annular shape see fig1 and 2 welding tips 20 22 preferably have flat contact surfaces as best seen in fig2 for good face to face electrical contact with the engaged surfaces of sheet 12 and 14 but each tip 20 22 has a hollowed out portion 24 and 26 respectfully to produce the annular contact tip face the cross sectional view of fig2 shows electrodes 16 and 18 in pressing contact with opposite surfaces of workpiece sheets 12 and 14 welding tip 22 of electrode 16 has a cylindrical relieved portion 26 so that the tip to surface contact with sheet 12 is annular in shape likewise the tip 20 of electrode 18 has a cylindrical relieved portion 24 which permits annular tip face to surface contact with sheet 14 as a suitable welding current is momentarily passed between welding electrode 18 and welding electrode 16 through the contacted regions of sheets 12 and 14 an annular pool of molten metal is first formed then as the electrodes are withdrawn the pool rapidly dissipates heat into the surrounding metal and solidifies into nugget 28 weld nugget 28 is in the shape of a donut.