Method of operating a welding machine and a welding machine

A welding machine comprising:

• a frame;
• a fixed electrode having a fixed position in the frame;
• and
• a movable electrode which has been mounted in the frame so as to be movable with respect to said frame, which movable electrode can be moved by a man-power operated operating member in the direction of the fixed electrode by transmission mechanism (3-12) arranged between the operating member and the movable electrode,
• wherein the transmission mechanism is provided with a cam which can be pivoted around a pivot pin from a starting position through a certain angle by the operating member to displace the movable electrode in the direction of the fixed electrode,
• which cam co-operates, during operation, with an adjusting member connected to the movable electrode, and
• the cam and the adjusting member co-operating with said cam being embodied such that at the beginning of the pivotal motion of the cam for displacing the movable electrode in the direction of the fixed electrode, the adjusting member is displaced at a higher rate than during the pivotal motion of the cam through the last part of the angle through which the cam is pivotable around the pivot pin for displacing the movable electrode in the direction of the fixed electrode.