Originally Posted by 12XU
What about the frames where lugs aren't present, but the welds are so smooth that the tubes appear to flow into each other?
There's a couple of ways to do that.
One way is called fillet brazing. There, you add a lot of brass at the joint and then file it smooth. Schwinn made a lot of frames like that. Sheldon has a good page that talks about it:
http://www.sheldonbrown.com/schwinn-braze.html
I have a fillet brazed Schwinn Super Sport built w/ Cro-Mo tubing and factory chromed. It's a sweet frame.
Jeff Lyon is a custom builder who makes nice fillet braze frames:
http://www.lyonsport.com/
You can also weld a frame and grind the welds for a smooth finish.
Real TIG artists, like the guys who make IRO and Kogswell TIG'd frames, make welds that look good.