At 08:42 PM 11/3/99 -0500, you wrote: >I made a brass gnomon with hand tools using a small plate of 3/16" brass. >I glued paper to the brass and transferred a sort of scrollwork pattern to >it and then cut it with a combination of hacksaw, fretsaw, drilling and >assorted files including needle files. It came out looking fine. > >At that point I thought I might be able to braze or silver-solder a sort of >foot-piece perpendicular to it. This would then be screwed to the dial >with small screws. I had a small amount of experience silver-soldering >small pieces, but was not able to do this both because of lack of technique >and lack of a hot enough flame. I ended up taking it to a nearby welding >shop and having it welded/brazed on. They did a reasonably good job, and >it all worked out in the end but I was disappointed not be able to do it >myself. > >What kind of torch does one need to braze a two pieces of 3/16 brass >together using brazing rod for filler, and what kind of flux should be >used? I tried using a boric acid solution and a torch with oxygen and mapp >gas but was not successful. And how do you do this without burning up the >brass? > >Jack >
Why not use low melting point solder? The tricks are, IMHO: 1) Use as little as possible 2) Good surface preparation with a close fit. 3) Good fixation of the parts to be soldered (I use the 1/16" pins) 4) Careful planning, especially if you are going to solder several small parts in turn (heating one joint will make another come apart if you are not careful) 5) I use ordinary plumber acid flux 6) Put little pieces of solder one side of the joint (I sometimes flatten them with a hammer and cut them to make them even smaller and allow the shape to correspond to the line of the joint). 7) Heat the joint *from the opposite side* to make the solder flow towards the heat and be sucked into the joint. Thus little is seen on the outside to clash with the appearance of the brass. 8) Ordinary butane torch has always done for me. For slightly hotter flame use the MAPP gas. 9) I have tried brazing and gave it up as it is a) considerably more difficult, b)causes heat distortion and heat discoloration. The melting point of brazing material is rather close to the melting point of the brass itself. I have melted a few gnomons... 10) I cannot envisage a condition where in ordinary use (sundial gnomon) a solder joint would not be strong enough. I do use a slightly thinner 1/8" brass... Mike Koblic, Quesnel BC
