Patent ID: 8338738

Claim:
A method of welding a projection bolt, the method comprising: inserting an end portion of a projection bolt held by a holding head of an advancing-retracting feed rod into a receiving hole of an electrode by using an advancing action of an insertion driving unit when the feed rod is located at an advanced position; applying a pushing-out force from the holding head to the projection bolt held at an insertion position to complete insertion of the projection bolt into the receiving hole; retracting the feed rod; advancing the electrode toward a steel plate part on standby; and after said advancing the electrode, welding the projection bolt to the steel plate by carrying out pressurization and energization, wherein said advancing the electrode is performed in response to a signal generated upon the insertion of the projection bolt into the receiving hole and a signal generated when a welding point on the steel sheet part to which the projection bolt is to be welded is aligned with the electrode, wherein the pushing-out force is exerted by applying an air blast, and wherein the pushing-out force is applied to the projection bolt inserted into the receiving hole to complete the insertion of the projection bolt into the receiving hole, and the application of the pushing-out force is continued until the feed rod returns to a midway point on a return stroke thereof.