obtained by the same proceas, but by substituting a mild steel pot for the cast iron one. Have the pot made by riveting and welding, as shown in Figure 127. Heat the parts in cyanide melted therein, and quench in water that is being agitated, as before described. The first time such a pot is used the parts will come out as hard as though treated in a cast iron pot—but parts heated in it thereafter will come out soft, but colored. Therefore, if coloring only is wanted, the pot should be heated for a half hour before putting in the cyanide.

Cyanide burdening is, in the final analysis, merely a substitute for the more satisfactory, but more expensive and difficult processes using charred bone .and leather. Yet it is often the only process readily

available in the small shop, and if extremely deep hardening is not essential, is quite satisfactory. But be careful Avoid put:ing articles into melted cyanide with any moisture on them—it will sputter and fly like melted lead. I have seen a dog die almost instantly when half a grain of cyanide was dropped into his eye. A photo-engraver accidently took a drink of water from a glass that had a few drops of cyanide solution in it. He started to walk out of the developing room—and fell dead with his foot in mid air and the glass in his hand.

SOME HARDENING KINKS: For drilling glass, chilled iron, hardened steel, etc.,—a Springfield receiver, for example— take a new drill that is well sharpened and has never been heated to cherry red. Dissolve zinc in muriatic acid to saturation, then add an equal quantity of water. Heat drill to dull cherry red and quench instantly in this solution, until cool. Use drill without further sharpening. Wet the drill point with rurpentine when drilling very hard steel or glass.

Small drills may be made of any piece of steel wire, by filing to shape. Mix 4 parts powdered rosin, 2 parts fish oil and 1 part tallow, heated together to melting point. Heat drill to dull red and dip iqto mixture, leaving it until cool. Reheat to red, and quench in culd water. Repeat two or three times, and the drill will easily cut glass.

A short piece of cast iron pipe, with ends threaded for caps, sometimes makes a handy substitute for cast iron box for casc iurdcning

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