John, back on the subject of tricks to tack. As you say, often when you try to melt to edges, and get the pools to wet together into one, surface tension causes the pools to ball up and retract away. The solution is to Zap the joint with a very short duration, high current pulse, at a very short arc length. You need high frequency arc starting and a foot pedal to do this. First you need the two edges to be in contact with each other, and it helps if the edges are square and sharp, not rounded or chamfered. To make the tack, you need to have the tip of the tungsten electrode very close to the joint, and equally pointed at both edges. It is best to rest the torch on the gas cup, so stick the tungsten out the right distance to allow you to do this. Set the current at about 150 amps. Get a preflow of gas going by tapping the foot pedal while holding the torch away from the work. Quickly position the torch while the gas is still flowing, and hammer the foot pedal quickly on and off. Adjust the current and on time to adjust the size of the tack weld.