Most Jeffsons are built with lugless fillet brazing (see below), but lugged construction is still possible and offers a great range of designs and finishes.
Lugged joints are of course very strong, and make for consistent and reliable joints with excellent fatigue resistance. Frame repairs are easy too as the frame can be repaired by reheating the joint and removing a damaged tube.
Some also feel that lugged steel frames are going to be heavier – after all, look at that extra metal being used. But the truth is that the weight differences between lugless and lugged frames are minimal. This is because lugless frames have heavier gauge tubes at their ends to compensate for the stress concentrations that lugless construction creates. In contrast, lugged construction allows thinner end butts, which compensates for the extra metal of the lugs.
Fillet brazing (luggless)
“Fillet brazed” has nothing to do with fish, but derives from the French word for ribbon. Fillet brazing is a technique where the tubes are joined without using lugs or welding. A brass brazing rod is used in the process and with several passes creates a small mound around the joint called the “fillet.”
Fillet brazing is especially popular with riders buying Jeffson frames, for three key reasons.
- Versatility: Fillet brazing enables us to join tubes of different diameters and shapes that lugs may not be able to handle or even be available for. After all, why buy a custom-made Jeffson frame with your own chosen geometry and then be restricted to only those angles and tube sizes that lugs are available for? For example, it’s very difficult finding lugs that will fit modern compact frame design.
- Reduced Temperature: Steel tubing develops weaknesses when heated, and fillet brazing means that the temperatures used are around 100degrees C cooler than for traditional welding. Therefore, it never takes the steel to its critical melting point and stresses are reduced. This also means that fillet brazed frames often survives crashes better – always a good feature for mountain bikes!
- Good looks: Fillet brazing provides a seamless transition between tubes, giving an elegant and contemporary finish as shown on the Jeffsons below.