Fillet brazing vs. TIG welding

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." I.E., 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. Of the seven models of steel tandems we build here at Santana, only the Noventa is still fillet brazed.

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). However, because our fillet-brazed Noventa uses stronger and thinner Columbus NivaCrom tubing, it remains lighter than a TIG-welded cromoly frame. For an even lighter steel frame we could TIG-weld a Noventa, but since weight freaks (as opposed to workmanship freaks) prefer our lighter and less expensive aluminum Sovereign, we don't produce a TIG-welded Noventa.

Because a properly fillet-brazed frame is the ultimate hallmark of a skilled framebuilder, the best reason to buy a fillet-brazed frame is because you value the artistry and can appreciate the builder's skill.

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