Brazing Copper Rod.
—For uniting two pieces of copper rod, 1⁄4 in. or 3⁄8 in. in diameter, first prepare the joint as at A in [Fig. 64], and file the surface of the copper clean in the immediate vicinity of the joint. A mixture of borax and water and spelter should now be applied to the joint, which should rest on a small heap of broken coke, the coke being also built round it. The flame of the blow-lamp should be directed at first on the coke surrounding the joint, and then gradually brought to bear on the joint itself. If necessary, add a little more spelter before any of it fuses, and when the copper begins to get red hot, throw just a pinch of dry borax on the joint to facilitate matters.
Fig. 64.—Dovetailed Joint in Copper Rod
Fig. 65.—Dovetailed Joint in Key Stem