Types of Lug
Traditional stamped lugs (aka pressed lugs) are formed by pressing sheet steel over a mandrel, bending them to shape, and then welding the seams. These lugs are of constant thickness resulting in stress risers, if large amounts of file work are not done to alter the thickness of the lug. They are easily identified by the visible seam.
Lugs used today on higher performance bicycles are investment cast (aka lost wax process). Copies of the lugs are made in wax, and they are attached together into a "tree". The tree is surrounded by ceramic and fired in a kiln, thereby melting the wax and setting the ceramic. Finally, molten steel is poured in to produce the lug. Cast lugs have many advantages over stamped lugs: they allow much finer detail, tighter tolerances (and correspondingly less manipulation and file work), and more accurate angles, and they can be made from superior materials (chromoly or stainless steel). The disadvantages of cast lugs are few: casting doesn't allow for long points or cutouts (done for aesthetic appeal), it is difficult to bend the lug to change the angle (requiring framebuilders to order lug sets that precisely match the desired frame geometry), and they are more expensive.
A relatively recent trend has been toward the use of stainless steel for investment cast lugs, as shown in the picture on the right. These lugs do not require painting, but must be brazed using silver filler rod, which necessitates much better heat control and better fit of lug to tube.
Cast lugs are found on higher quality production bikes, and virtually all custom bikes now made; stamped lugs are found on less expensive production bikes, and older custom bikes. Lugs are usually stamped with a letter or symbol code identifying the maker, and possibly the angle.
Read more about this topic: Lugged Steel Frame Construction
Famous quotes containing the words types of and/or types:
“Our children evaluate themselves based on the opinions we have of them. When we use harsh words, biting comments, and a sarcastic tone of voice, we plant the seeds of self-doubt in their developing minds.... Children who receive a steady diet of these types of messages end up feeling powerless, inadequate, and unimportant. They start to believe that they are bad, and that they can never do enough.”
—Stephanie Martson (20th century)
“The rank and file have let their servants become their masters and dictators.... Provision should be made in all union constitutions for the recall of leaders. Big salaries should not be paid. Career hunters should be driven out, as well as leaders who use labor for political ends. These types are menaces to the advancement of labor.”
—Mother Jones (1830–1930)