The end cap, sometimes called a “butt cap”, serves to protect the end of the handle from impact and acts as a “ferrule” to help prevent the handle from ever splitting. In this scenario, it also serves to conceal a counter sunk nut on the end of a threaded tang.
In this example I’m using bronze.
#1. This is a two part fabrication, a brazed oval ring with a good friction fit to the end of the handle and a swedged plate, Approximately 1/8 inch thick, with a slight dome.
#2. Mark a line with a scribe around the inside of the hole and trim the swedged plate to the line at a slight angle with a grinder or a file. The taper will help achieve a snug fit and prevent the piece from slipping or sinking during silver brazing.
#3. Tap the piece into position with a hammer.
#4. Silver braze the piece in place.
#5. Pickle the end cap after brazing, clean up with files and sandpaper and check the fit.
At final assembly the end cap can be secured into place with a good high strength epoxy paste like J-B Weld. Since the end cap fits over the end of the handle mechanically with a nice tight friction fit, unlike a standard butt seam, it can’t be pulled, sheared or knocked off once the epoxy sets.