Originally Posted by
WheelNut2
Scooper- Is there a particular part of the lug/joint you start with when you tack braze? Multi spots? A cross pattern, like when torquing something with 4 bolts? Thanks for any insight.
Regarding the brazing sequence, I use the process recommended by Reynolds Technology in its
531 Technical Advice data sheet, starting with the bottom bracket shell and working clockwise:
Originally Posted by Reynolds Technology
When the tubes are fitted into the lugs, care should be taken that the assembly is not in a state of stress. Brazing should be carried out in the following clockwise sequence:
• bottom bracket
• down tube/head tube joint
• head tube/top tube joint
• top tube/seat tube joint
This sequence obviates the danger of a stress raiser being created at a major shock point.
When brazing frames made from Reynolds 531 Tubing, the joints should be pre-heated, and after brazing the cooling should be controlled and not forced. Brazing must be carried out in a shop free from draughts.
Great care must be taken not to overheat the material, or to heat too large an area of the tube. Overheating will lead to burning or to brass inclusion (where the molten brass or bronze enters the grain of the steel), either of which will make the tube brittle.
Setting, when necessary, should always be done cold.
I usually tack braze each lug to tube join in four spots 90° apart while the frame is in the jig, then remove the assembly from the jig and fully braze the down tube-to-BB shell and seat tube-to-BB shell. I "pull" the down tube and seat tube into alignment using heat from the torch and checking alignment on my alignment table. Then I fully braze each successive join as described in the Reynolds procedure, checking and adjusting alignment as each join is brazed.
This method works for me, and ensures there is no cumulative stress built into the frame as often occurs if all joins are fully brazed in the jig.