Brazing, a lower temperature process than welding, uses a bronze rod to create a fillet–a French word for ribbon–pronounced FILL-it (not fill-LAY). It was previously thought higher welding temperatures would ruin good tubing. We now know because welding is faster, the damaging effect of higher temperature is mitigated by shorter heat duration. While disagreements about the relative merits of lower temperature vs. shorter duration continue, a properly fillet-brazed joint will certainly have greater accident “survivability.” For example, if you run into a tree or parked car, a fillet-brazed joint is less likely to fail. Either joint will withstand decades of normal use.
Because the bronze fillet is softer than the steel tubing it joins, a skilled craftsman can sculpt a brazed joint without cutting into the tube. Please note that the quality of this sculpting (or craftsmanship) is highly variable–look for large smooth fillets with compound radii and long feathered edges. Beware of “overbite.” Overbite, a result of hurried or sloppy work, is where part of the steel tube has been carelessly filed away at the edge of the fillet. This creates a stress riser that can lead to frame failure. Unfortunately, overbite is a common flaw found on many fillet brazed frames.
Unavoidable downside of fillet brazing #1: Price.
Because fillet brazed construction requires much more time and skill, the price of a properly fillet brazed tandem frame will be $300-$500 higher. If the price differential is lower, inspect the joints carefully before taking delivery. Because of the price, most bicycle customers choose a TIG welded frame.
Unavoidable downside of fillet brazing #2: Weight.
A filleted joint, like a lugged joint, is slightly heavier than a TIG-welded joint (4oz penalty on a single bike, 12oz penalty on a tandem).
Because a properly fillet brazed frame is the ultimate hallmark of a skilled frame builder, the best reason to buy a fillet-brazed frame is because you value the artistry and can appreciate the builder’s skill.
If you need more information about fillet brazed frame, I can recommend that you can visit the website of MAXWAY Cycles Co., Ltd… The company is specializing in producing kinds of bike frames such as city bike frames, cyclocross bike frames, fillet brazed frame, MTB bicycle frames, trekking bike frame, etc. More details about bicycle frames, please feel free to send inquiry to MAXWAY.
Article Source: http://www.gtgtandems.com/tech/brazing.html