So last week I brazed some brake bosses to the fork of the new/old Raleigh. Brazing is a process of joining metal in which two pieces of a certain material (in this case steel) are held together by a joint of a different metal with a lower melting temperature (in this case brass). Before the steel fork leg and the steel brake boss could be joined, they both had to be cleaned to avoid contaminating the brass fillet. This was achieved by sanding them down to bare metal, and by applying an acidic flux that also serves to draw the flow of molten brass.
After prepping the parts and holding them in place with a temporary fixture, the oxy-acetlyn torch comes out. By mindfully heating both steel elements to roughly the same red-hot temperature, you can ensure that the brass rod will melt and meld to both of them easily. What needs to be kept in mind are the different properties of the parts to be joined that will affect how quickly they heat up, how long they hold their heat, and how the blazing jet of flame will push the molten brass along their juncture.
Once the joint is brazed, the fork is functionally done. However, it is sthetically far from perfect. (An aside, I just really wanted to use the ” character, even if it’s not entirely correct. !)
The torched flux becomes very hard, but is easily removed by soaking in water. After sitting in a bucket for a day or two, Paul brought the (only somewhat) cleaner fork to me at the bike shop where I spent several hours after closing filing, riffling, sanding, and smoothing out the fillets. The brass looks much better now, and I’ve a much higher appreciation for masterful brazing that requires only the minimum of cleanup.
Brazing for the first time was very satisfying, and the process of juggling multiple metal and mental pieces was no more difficult than I imagined. That is to say, I believe this is something I could come to do well with practice. Loose plans have been made among like-minded cohorts to work in tandem on some initial frame building this summer. That is to say, we have most of the tools and materials, and we have enthusiasm.
Tomorrow I’m bringing the rest of the frame over to Paul’s shop so I can braze some brake bosses to the rear as well. Hopefully I’ll remember to take some photos of the finished fork bosses, and maybe some shots of me wearing wicked cool welding glasses as well.