Filed In: Process
December 09, 2019 | Chris Blandford
All right, time to tack and braze this little frame together.
9. Tack Frame in Jig
10. Quick Alignment Check
11. Braze Frame Free of Jig
To tack the frame together, I begin by applying blue flux to the tubes and loading them into the jig. I apply a full coat of flux--enough to last through the tacking and the brazing. I also flux about an inch up into the ends of the mitered tubes. Using the same 203 tip, a neutral & rumbling flame, and 1/16th bronze rod, I tack the tubes together along the frame’s centerline. Here’s my tacking sequence:
In short: obtuse angles first--from the BB up and around to the seat tube, and then acute angles--back down and around. The general thinking here is that tacking the obtuse angles first will minimize any pull-apart on the opposing side of the miter, as the bronze will pull the tubes more “into” one another. For chain stays, however, I tack the outside (acute) sides first, then the obtuse sides. This is done to minimize suck-in at the rear dropouts and to keep the rear spacing as designed. (For this little bike, I’m waiting to connect the top tubes along with the seat stays, mixte-style. So, I skipped tacks #3-6.)