1. A method of monitoring the quality of percussion welds made on a percussion welding machine comprising: sensing a weld current passed through parts to be welded, one of which has a nib in contact with the other, as said parts are heated and said nib explodes, and as forge pressure is applied to impact and unite said parts; measuring nib time from the start of said weld current to nib explosion and dwell time from the nib explosion until said parts are forged together; and determining weld quality by comparing said nib and dwell times to preselected acceptance limits.