Soldering Notes: After drilling or punching the hole in your vesselscuff up the contact areas of both the vessel and the flange using some 100" grit sandpaper then wipe off residue with solvent on a rag. Apply acid flux such as Harris Stay Clean Liquid flux to both surfaces. Lay the flange centered over the hole ensuring that the radius in the flange most closely follows that of the vessel (You may want to mark top and bottom with indexing marks on top of the TC flange to make this easier). Once you are happy with placement, use small C-clamps inserted through the hole to firmly clamp the flange in place and to draw in any gaps due to radius mismatch. Using an LP or MAPP torch, warm the vessel walls first keeping the flame moving, avoiding the flange for a few minutes. Then concentrate the heat on the TC flange itself, avoiding burning the flux as much as possible. The ideal temperature is reached when your solder melts when applied to the joint between the flange and vessel and NOT when the solder wire is directly heated by your flame. Solder should be quite liquid and start drawing into the gap. Work the solder around the entire flange, reheating the flange briefly as necessary. This process is shown in a instructional video at the bottom of this page.
Disclaimer: Soldering is not horribly challenging, but you should be moderately handy if you're going to attempt this. If you've never soldered copper plumbing with success before, you may want to do some practicing first. Acid flux is dangerous to handle and the fumes are toxic. Please use a respirator and/or solder outside or in a well ventilated area. Torches make things very hot! DUH... typical silver bearing solders with 3-6% silver content melt just under 500F and the flange will stay hot for several minutes after you remove the heat. Just be careful!