I am fortunate to have a DoAll Blade Welder that can weld 1" blades. The process is called Flash Butt Welding. In the shops of the company I work for we also have "blade welders" that can weld railroad rails together. These can weld 155#/yd rail (8" tall x 6-3/4" base) in about 90 seconds. These welders can weld 80' rails into 1460' strings which are loaded on rail trains and delivered to the installation site. Power service to these machines is 460VAC at 800 Amps and they weigh about 75 Tons. Likely too large for most home shops.

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But before the DoAll welder I had to braze or more correctly "Silver Solder" Blades. Just as in painting a car, the prep work is everything and if done correctly the soldering is the easy part. I found it best to not grind the scarf joint before soldering. I grind the "tooth set" from the faces of the blade to be joined and lap the to blade ends together for a distance of 1/2" to 1". The goal is to have a "no gap" joint. Don't get crazy here, if you lap too much the finished repaired blade may be to short to go over the saw wheels when you are done. Even in FBWing broken blades back together the results can be too short. If this is suspected to be the case I will weld too broken blades together and cut out a section to get the correct length needed to fit the saw. The left over material is saved for the next time length has to? be added, just be sure to have at least 10" or 12" between joints.

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A dirty grinding wheel will cause soldering problems also. The wheel should be new or newly dressed to be sure that things like copper, brass,? aluminum,? stainless, etc. are not deposited on the surfaces to be joined by the dirty wheel. The faces to be joined should be liberally fluxed and a piece of Silver Solder "Foil" place between the lapped ends of the blade. Heat gently until the solder is seen to melt and suck into the join. Remove the heat and immediately press the sandwiched blade flat with a piece of preheated metal.

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You now should have a lapped blade that has no chance of going thought he guides unless you run the saw real fast. To solve this, bend the now annealed blade at both ends of the lap until the main portion of the blade on both side of the lap is in a straight line. Now grind the protruding lapped end flush with the main body of the blade. Go slow so you don't over heat the ends of the lap and melt the solder loose while checking the thickness frequently. Ideally you would remove the same amount from both sides but there is a bit of leeway as long as the overall thickness is correct. Lightly grind the back also to level the joint.

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I was never really successful until I adopted this method. It is just about impossible to freehand grind a tight scarf joint on the ends of the blade, especially without burning the ends. The success or failure of a soldered joint can be measured by the thickness of the solder interface.

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So now I will go back into hiding like a "lurker on a porn site" until the next time.

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gary