#1. File a “V” notch in the end of the tang with a triangular file and file or grind one end of the threaded piece to match as perfectly as possible. Make sure the area and surfaces to be joined are clean, and free of scale and oxidation.
#2. Use hard grade/high temp., silver solder granules. The granules are made by fluxing pieces cut from sheet or wire solder and then heating them with a torch until they melt and pull into tiny spheres. The granules can then be transported with a stainless steel soldering pick. This is done by melting flux on the tip of the pick and the granule simultaneously and using the tackiness of the flux to hold the granule.
#3. Flux the joint and position the granules.
#4. Heat the steel, (tang and threads), evenly with a torch until the solder flows into the joint by capillary action.
#5. Pickle and wire brush the area for clean up. Check the seam and file off any excess solder if needed.
For general information on brazing and the strength of silver brazing, click here.
For further study, also see what MS Wayne Goddard has to say, more information.