Framebuilding with Dave Bohm: Day 3

Today was all about learning to braze. The first order of business was to prepare a lug and mating tubes so we could try our hand at silver brazing.

Dave brazed the first lug to show us how it’s supposed to go. Cooper stepped up next and really hit it out of the park. His shorelines were very clean and he didn’t nuke the joint, which is so common with inexperienced framebuilders.

Finally I gave it a go. Although I could have done better, I too didn’t overheat anything. I could have done better however smoothing out some of the blobs on the lug edges.

After we soaked the flux off our masterpieces, Dave asked us to saw them in half to inspect how well we were able to draw silver into the recesses of the joint. We both did a decent job with some room for improvement. Dave emphasized how important it is to really fill a lugged joint with filler to create a secure bond between lug and tubes.

Cooper goes to town on his first lugged joint. He did a kickass job.
Cooper goes to town on his first lugged joint. He did a kickass job.
My first brazed lug in probably four years turned out pretty well. The thin gold line is the silver that penetrated the deepest recesses of the lug joint. The black void is a result of using an old lug with an imprecise shape.
My first brazed lug in probably four years turned out pretty well. The thin gold line is the silver that penetrated the deepest recesses of the lug joint. The black void is a result of using an old lug with an imprecise shape.

After another round of lugged brazing, we jumped back to practicing our fillet brazing skills by joining a pair of tubes. In many ways fillet brazing is easier. For one you can see the filler the whole time you’re adding it, unlike with lugged brazing, where most of the filler is hidden inside the lug. Controlling bronze is also a bit easier as it has a thicker consistency when it’s in liquid form. Silver turns really thin and travels quickly.

After a break we then got to practice bonding a dropout to a chainstay. This can be a tricky joint because the dropout has far more mass than the little end of the chainstay. I liked Dave’s method of tacking the points of the slotted chainstay before adding the bulk of the bronze. The tacked bit of bronze helps protect the fragile ends of the tube from quickly overheating.

Dave advises Cooper how to best braze up the dropout to the chainstay.
Dave advises Cooper how to best braze up the dropout to the chainstay.
Cooper adds heat and bronze to the dropout / chainstay connection.
Cooper adds heat and bronze to the dropout / chainstay connection.

Cooper and I did a pretty good job of locking the suckers together. At the end of the day we joked that once we actually started joining our frame together, we’d start making the typical newbie mistakes that, for the most part, we’ve been lucky enough to avoid. Once the heat is on, we’ll see if our good fortune continues.

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