Wow what a load of crap some have so happly donated here!!! First lets start with Tom, Tom had a lot of good ideas except for some statements like: "The TIG weld is as strong or stronger than a lugged unit although both types of construction are plenty strong." That's pure hooey, the lug construction is every bit as strong and stronger then a tig weld; the reason MTB went that route was to save money on construction cost-THATS IT!-which Tom alludes to later in his post!

The second statement Tom makes: "One big reason that lugs dissapeared is that a set of lugs will only accomodate a few frame sizes due to the different frame angles needed to make extra small or extra large frameserts. Hence, the expense to tool numerous sets of lugs would result in a frame that would be more costly." Where did that come from? Bike manufactures for years were making bikes from the smallest to the largest frame size's and used lugs; the molds for all these various angles with lugs were already made so making the frame to fit whatever size rider was never an issue.

Tom's third statement: "Lastly, without lugs you have a lot more freedom insofar as the diameter and shape of the tube. With lugs, you're forced to use steel and small diameter steel tubes. Without lugs, you can vary the shape and diameter greatly using various materials (aluminum, titanium & steel)." This was a half true statement-the wrong part was the diameter and shape of the tube...kind of true, but there were oversize tubesets called OS and MAX tubes that had lugs available for them, and some such as Colnago used a tube with a fluted shape to it and they had lugs to fit it. Making a lug of various shapes, sizes and designs is not a problem with wax castings, but to keep complication down they limited it to 2 different tube diameters and limited it to tube shape-mostly round except for the Colnago.

Then Astra said that lug construction is heavier, problem is with a welded frame they have to have the ends thicker to buttress the tube when it's welded so the thicker ends almost negate the lugs weight and still is not as strong as the lug.

Read the sites I posted earlier, plus here's more for your entertainment pleasure: http://www.henryjames.com/faq.html
http://www.epinions.com/content_1176608900
http://www.worldclasscycles.com/JACKSON-HOME.htm (read fabrication methods).