To me... there are two problems... the first, not enough heat and solder used and the second, not enough surface area to make a good joint.
What torch are you using ? I would use an Oxy/Acet Torch with a Rose Bud tip to spread out the heat, as stated above you need to get the heat all around the piece as evenly as possible.longevity. You need to add a reenforcement in the back of the piece. Slightly heat an extra piece of brass and form it slightly to the rear of the frame once you have the piece formed you need to use liquid flux, an acid based flux is the best, and should allow for a quick flow of solder. Brush the liquid flux on heat it up and watch the flux go somewhat clear then apply the Silver Solder, the good stuff not the 2% stuff. You will need a solder diameter that will supply enough solder to the heated point to make the joint strong enough. The surface area you are tryin to connect, if just rough ends, is too small to maintain a connection with When clamping the piece, extra heat needs to be applied to compensate but there is a limit so go slow. One more thing, I am not sure what the melting point of Cast Brass is... Im thinking higher than the Silver Solder... BUT we don't know the material content, I do know soldering copper and brass pipe is heat until the solder flows then remove heat while still applying the solder. OK other ideas: 1) What about just making a support, form it to the back of the frame as best possible, clean things up, maybe even use some very small screws and secure the support before solder the front and only the front. The front is flat so a slight chamfer on the pieces, fill chamfer and then clean up the front. Keep the chamfer small, and unless the boss want to get away with a broken piece, it should look ok. 2) Make a "U" shaped piece of brass and solder it to the front of the piece, clean, liquid flux. Add a similar piece to the other side, same place, shouldn't look too bad. 3) Maybe combine 1 and 2 ! That's all I can add to this topic, thinking too much, Silver Soldering is like Brazing, heat is your friend to a point and sometimes it is better to take it to someone that know the material and how to fix it the best way !
Do It Right The First Time !
GrevB Location: SoCal, USA