In accordance with well-known rules, the immersion in the hardening bath should be done with the point first, slowly and vertically up to above the riveting hole.
Hardening Without Scaling.
Hardening With Glycerine.
II.—Glycerine, 8,000 parts, by weight; cooking salt, 500 parts, by weight; sal ammoniac, 100 parts, by weight; concentrated hydrochloric acid, 50 parts; and water, 10,000 parts, by weight. Into this liquid the steel, heated, for example, to a cherry red, is dipped. A reheating of the steel is not necessary.
To Remove Burnt Oil From Hardened Steel.
Various Recipes:
To Put An Edge On Steel Tools.
To Restore Burnt Steel.
To Remove Strains In Metal By Heating.
If a piece of metal of any kind is straightened cold and then put into a lathe and a chip turned off, it will be far from true. Before turning, it was held true by the strain of the particles on the outside, they having changed position, while the particles near the axis are only sprung. The outside particles being removed by the lathe tool, the sprung particles at the center return to their old positions. If, after straightening, the metal is heated to a temperature of 400° F., the particles settle together and the strains are removed.