Check out the video of the process at the end of this post!
Sheets of sterling silver are marked out with calipers to slightly oversized dimensions. The flat section is measured out about 2 mm wider to give the ferrule tangs to allow handling with pliers. The final 1 mm or so of fitting the ferrule to the frog is pressure fit and the tangs allow grip without marring any part of what will be the finished ferrule. To cut the silver, I like to use jewelers shears rather then a jewelers saw. The cuts are straighter and produce less waste with the shears.
The silver pieces are then flattened with a jewelers anvil (a flat and hardened piece of steel) and rawhide hammer to prevent marring. It is then followed with a file to produce a perfectly flat and clean surface for soldering. I also square up the edges of each piece with a file and small machinists square.
The round section is formed with a mandrel and counter form. These are tools I made, machined to specific dimensions, to produce the desired radius and dimensions of the ferrule. Once formed, the height is filed to the desired dimension.
For this video, I had just cleaned the pieces with alcohol, sometimes I use an acid known commonly as jewelers pickle. The point is to remove any oils and dirt to ensure a perfect bond. I flux the joints and tie the part together with iron binding wire making sure to square up the parts. Lastly, short lengths of fluxed silver solder are placed inside near both joints.
A jewelers torch is lit and set with a reducing flame. Heat is slowly introduced to the entire ferrule. As soon as the solder starts to flow, the heat is focused on the outside of the joints. This draws the solder through the joints and any excess solder is built up on the exterior of the joint. The extra solder is easily filed away when executing the final shaping of the ferrule. The idea is to minimize the amount of solder clean up to the interior joints of the ferrule, for both speed and cleanliness.
Once sufficiently soldered, I quench the ferrule in hot jewelers pickle. This cleans off any scale from the soldering process and softens the silver a bit for additional forming. As the ferrule gets worked onto the frog, it will eventually work harden. It can also be hardened later in the process, during the final fitting to the frog, by reheating it and letting it air cool.
After quenching, the binding wire is removed and lightly cleaned. The ferrule will get squared up once more and brought closer to final dimensions. It is now ready to be fit to a roughed out frog!