Yeah, it is, but the way lugless, brazed frames were done was that the tubes were mitered EXACTLY for fit, and then silver-soldered (or brazed) together. Usually, a milling machine was required because of the close tolerances that were needed, although I heard tell of someone that could do it by hand!

My tuppence worth. Lugged frames are normally heavier than TIG welded. Brazing should affect the tubings strength less, but it's still quite easy to overcook the tube. Tig is a more localised heat, which is better, unfortunately it normally effects the tubings strength adversely. Fancy air hardened tubes are overrated - there's no such thing as a free lunch, check all the specs of the tubing used (if you can find them) as UTS goes up, so elongation and fatigue resistance decreases.

I have examples of quite a few different types of steel frames,lugged cr-mo, tigged cr-mo, tigged 853, brazed T45, brazed 753. The only one I've had problems with is the TIG welded 853 frame.

i don't know much about the process, but here are some pictures... I assume you meant this particular peugeot (PH12) Scroll down to the year 1983/ph12
click here

1)Lugs in no way restrict the geometry or tubing a builder can use, since said builder could make their own lugs if needed.

2)Lugless brazed frames actually use internal lugs, no one in their right mind would ride a bike made of brazed-together tubing without some reinforcement.

3)Lugged and welded frames have both been used with great success, frame choice is more a matter of personal preference than functionality.

1) Yes, lugs are restrictive. They can be manipulated somewhat but overall they are not as flexable as TIG or fillet brazing.

2) Fillet brazed frames are held together entirely with melted brazing material - no internal reinforcement. These frames have been around for about 100 years so no worries.

3) Agree :) Well said:)

1)I suppose it is impractical, but custom lugs could be made for any frame geometry or tubing desired.

2)I stand corrected.

3)Just stating the obvious :)