I often like to ball the tip of my tungsten before welding on AC, especially if I'm doing a lot of parts and want my electrode to keep the same geometry for repeatability. I'm using 2% lanthanated and having problems with kind of divets or pores in the surface of the ball on the end of the electrode. The ball is more or less round in overall shape but its surface isn't dead smooth like you get for example on green pure tungsten. What I notice is that the balled tip just doesn't hold its shape over time as consistently when it starts off with these pores and in fact the instability of the tip is visible whilst welding. I see it start to melt and move around. At the same amps on the same part, if I managed to ball the electrode nice and smooth from the start, it will hold up way better.
So I'm wondering what factors determine how the tip balls up. Would really appreciate any tips here. One limitation is that I don't have a foot pedal, just an on/off switch (I live in Germany and foot pedals really aren't commonplace in the industry here) which means I really have to set the current just right for the electrode to ball up the amount I want it to.
A quick anecdote about balling the tungsten - our sales rep for our welding machines at work (Rehm) came by a couple of weeks ago and recommended that I use a piece of stainless when balling the tungsten, as opposed to aluminium. He said that the chrome and nickel from the stainless precipitates onto the tip, coating it, which increases its heat resistance and gives a more durable electrode tip. Well... I'll let you decide for yourselves as to whether that makes any sense whatsoever...