Ok, so a few more class sessions have come and gone and I think I'm starting to get the hang of it. Plus I have returned with a few images to show, and some other unrelated questions. My technique can't be too bad at this point as I even managed to weld a piece of 18 gauge steel sheet at a right angle to a 1/4" thick steel plate and not burn through the 18 gauge piece at all across a four inch long bead... the weld didn't fail when I hammered the crap out of it, either, so I think I'm getting somewhere!
First off, thanks to everyone for their suggestions and advice. What really got me on the right track was turning up the current... I was a bit skeptical at first since I already had enough current to make a seriously wide bead... take it from me, one should never doubt the words of Ernie! The trick really is to hit the joint hard and fast to get a tight little bead at the point where both pieces meet, and then to move quickly across the piece. In fact it seems like you move a great deal faster than normal for things like stringers and butt joints... but, it does appear to do the trick. It has also helped that I'm working with thicker steel now... it's darned near impossible to learn on thin metal with something like this. Once I started getting the hang of it on thicker material I was able to move over to thinner materials, hence the aforementioned 18 gauge welded to a 1/4" thick plate.
I never did figure out the trick of melting off a small ball of filler to create the tack weld, though. The ball always stayed stuck to the rod, and would just creep up the rod and away from the arc. I did figure out a technique that worked for me, and it's been working well. I start an arc and just heat up the two pieces to be joined without actually melting them. Then I point the tungsten at the gap between the two pieces... the arc will naturally jump from piece to piece, or maybe even favor one piece over the other. Then you stomp on the pedal and give it a lot of current. Suddenly a puddle forms that flows between the two pieces. As soon as that happens, you release the pedal and you're left with a tiny, uniform tack weld with fairly minimal penetration but definitely enough to get the job done. I don't know how well that will work for others, but it's been working wonderfully for me on all types of joints and materials. Plus as I'm not using any filler rod I can use my free hand to steady my torch hand and get a very precise aiming as my hands naturally shake quite a bit.
Now then, some pictures and some questions. I'm not one to normally submit my work for public review due to a glaring lack of self-esteem, but I figure this will help me improve. First picture is of one of my lap joint beads that I think turned out quite well except for an odd dot in the middle of it... my guess is that it's a slag inclusion or something similar given the fact that the metal I was welding had an awful lot of stubborn mill scale on it, but maybe someone with more experience can tell me. I'm pretty sure I didn't dunk the tungsten there or anything like that, especially since I would have noticed the arc cutting out and the tungsten wouldn't look as uncontaminated as it does. The image can be viewed here:
Feel free to rag on me, though constructive comments are preferred. Next, a couple images of a T-joint I made. There's some rust on the bead now because it has been sitting around in some bad conditions, but the bead itself is still visible (except that the pictures themselves are a little crummy). Images are here:
I apologize for the poor image quality, in fact the second one is even a bit misleading as a result. The penetration is actually quite good and the welds are properly concave fillets without undercutting, but it's not enitrely evident from the images.
And last, three tungstens of mine that I'm proud to say I ground by hand, no holding fixture of any kind except my fingers:
The two on the left are lanthanated and the one on the right is zirconated. The middle tungsten was the one I used to create the above pictured joints. The left tungsten is actually not quite ground the way I like... I was in a rush grinding that one, the tip's a little bit dinged up. I've been pointing my zircon tungstens before using them on AC but blunting the tips a bit more than with DC use tungstens... it seems like I get a nice ball on the end that way that isn't so large as to cause the arc to get unwieldy, but I'd welcome any other point grinding suggestions anyone may have.
So that's my current progress, comments are invited! It's taken me something like ten weeks of class totalling maybe four to six hours a week of just TIG welding to get where I am, so hopefully I'm getting someplace worth being. Thanks!