Just a comment or two.
If you Google Do-All you can find instructions for the blade welders on their saws.
I silver solder my blades with a jig similar to the one a previous poster showed. Mine evolved over time and is nowhere as nice as his. One thing I have added that I find very helpful is a round carbon rod the end placed under the weld area level with the blade bottom. After I see that the solder is melted, I remove the flame and press down with another piece of carbon and squeeze out any excess solder. This gives you a flatter joint. The solder and flux I use was bought some 50 plus years ago to make a bracelet for my wife.