STEP 1: Tubes are each cut and shaped (“mitered”) to match the diameter of the tube to which they’ll be joined. Often this is done by machining and cutting on a lathe, but can also be done with simple hand files.
The tubes should fit together neatly and tight before they can be joined. These tubes depict a fillet-type joint. he amount of filler metal applied to each joint will depend on the rider’s anticipated body weight and the type of frame. Joints that will be subject to higher stresses will receive more filler metal than those that are less stressed.
STEP 2: Once the mitering is complete, the tubes are coated with flux before they are joined. Flux absorbs oxides formed during heating and promotes the smooth flow of the filler metals.
STEP 3: Using an oxy/acetylene torch, the flux and tubes are then heated to the proper heat range for the filler metal, which is about 1650 degrees F for nickel bronze and about 1300 degrees F for nickel silver.
STEP 4: Once the flux approaches the proper heat range, it begins to liquify and develop a “glass”-like appearance. Note the slight cherry-red glow just above the joint on the vertical tube. This means the joint is ready to braze!
STEP 5: The filler metal (nickel bronze pictured above) is added to the joint. The rod is directly heated by the torch to bring it near its liquid state, then heat is applied to the joint as the filler is added. Once complete, the joint is allowed to fully cool before the flux is removed by immersing in boiling-hot water. The joint can then be finished. Fillet-brazed joints like shown above will last for the life of the frame, usually many decades.