Tips on Brazing Carbide Tools with recessing and grooving tools
• Mill the shank portion of the carbide tools & lathe tools to achieve the tip seating surface, top rake face, front and side clearance angles.
• Maintain the width of the shank portion just underneath the tip at 0.2 to 0.3 mm less than the carbide tip size.
• De burr the cutting tools very carefully so that most of the tip seating surface is available to make a flat contact with the carbide tip and grind a 0.75×45 degree chamfer on the bottom and back end of the carbide tip.
• Carefully grind the base of the carbide tip and inspect for flatness of the ground portion to ensure proper contact with the steel surface while brazing.
• Use 50% silver brazing foil of 0.1mm thickness and cut the foil to size and bend it suitably so as to cover the entire brazing area.
• Degrease the carbide tip, silver foil and the steel shank and also ensure the seating area of the steel shank is free of burr and rust.
• Use a compatible flux which ensures no oxidation till 750 degrees centigrade.
• Mix the flux with distilled water to make a paste and apply it onto the tip seating area of the tool. Place the silver foil on the tip carefully and apply the flux paste again on the silver foil. Now place the carbide tip on the silver foil and allow it to dry at room temperature.
• Set the Induction brazing machine with a suitable coil to braze the tools and set the power tapping points in the machine to provide for a slow heating of the tool while brazing.
• Place the tool to be brazed in the Induction coil of the brazing machine and hold a steel pointer rod on the tip to avoid it from sliding away.
• Heat up the tool sufficiently till the silver foil melts [about 650 degrees C] and position the tip with the pointer rod centrally over the shank portion.
• Ensure not to overheat the carbide or the steel shank.
• It can be noticed that the steel portion reaches the desired temperature much earlier than the carbide tip. To ensure that both the steel portion and the carbide tip achieve the same temperature, use the pedal switch to switch on and off the machine so that the heat from the steel portion is transferred to the carbide tip and once they both reach than uniform temperature, heating can be restarted to go up to the melting temperature of the silver foil.
• Press the carbide tip onto the steel shank just as the tip starts to cool.
• Remove the cutting tool from the coil and place it in preheated graphite powder to ensure slow cooling of the brazed tool.