Abstract: A plastic welder that can be held and operated with only one hand. The supply rod or filler rod can be advanced into and through the heating tip of the welder by a trigger that can be actuated by the user with the same hand in which the grip of the plastic welder is held. No air assist is required, as a device is provided for reliably avoiding overheating of the plastic welder by intermittently interrupting the electrical current feeding the heating element at times automatically determined by a temperature setting selected by the user. The heating tip is formed of a major portion of steel infiltrated with a minor portion of copper. The temperature of the heating element with the welder in inoperative condition is maintained at a predetermined level above the temperature of the heating tip when the welder is operative and in use.