Keeping bosses straight
 

This is my second attempt at brazing on such delicate material and I have a question. To keep the bosses straight do you use a jig or did it get better with practice? I made the holes so I had to push in the bosses rather than just fall in, I filed out the holes on the strengthening diamonds so they fit around the head of the boss and then proceed to braze everything. I am mostly pleased except for one of the bosses if off a little. Not that it will be noticed but I will know it is there. I even managed to fill in a couple dings on the top tube.https://cimg7.ibsrv.net/gimg/bikefor...10a78f6815.jpg

https://cimg3.ibsrv.net/gimg/bikefor...f5fb3fcadb.jpg
Are the axis of the bosses off? Or are the tangs of the reinforcements off?

I don't bother with reinforcing "plates" although when I have used them I remember that care in their forming (the curve needs to be spot on) and care during the brazing are essential. Touching the reinforcement with the filler rod can be a help or hinderance, here practice certainly helps.

I do use a home made jig to insure the verticalness of the boss axis. The pilots are Al so they don't bond to the silver and are smooth to not become flux frozen in the boss. I did use my sloppy and small lathe. Here's a shot. Lastly is that I will file the top end of the boss square and flat to the tube regardless of how things turn out. Usually this is only a tiny "correction" given my piloted jig. Andy

It is the axis of the bosses that is off. I had the center line scribed on the tube to keep the tangs straight, and I did bump the first one with the brazing wire once and had to correct it. I went with the reinforcements because I feel they fit the age of the frame and they complement the nervex lugs. I have a few more frames I plan to do this to so I think I will build a jig similar to yours to help me. Thanks for your help


Dave

The jig I use doesn't do much to insure that the bosses are on the centerline of the tube. The drilled holes do that. Before I got an Alex Meade drilling jig I would drill a tad undersized and touch up the holes' locations with a chainsaw file. Then round off with the right size drill bit. This way I could correct for off center initial holes. Andy