3284. Engraving Mixture for Writing on Steel

3284.    Engraving Mixture for Writing on Steel. Sulphate of copper, 1 ounce; sal-ammoniac, 1/2 ounce; pulverize separately, adding a little vermilion to color it, and mix with l1/2 ounces vinegar. Rub the steel with soft soap and write with a clean hard pen, without a slit, dipped in the mixture.

3285. Tempering Tools

3285.    Tempering Tools. The steel is generally first hardened by heating it to a cherry red, and then plunging it into cold water. Afterward the temper is drawn by moderately heating the steel again. Different degrees of hardness are required for different purposes.

For very pale straw color, 430°, for lancets.

A shade of darker yellow, 450°, for razors and surgical instruments.

Darker straw yellow, 470°, for pen-knives.

Still darker yellow, 490°, chisel for cutting iron.

Brown yellow, 500°, axes and plane-irons.

Yellow, slightly tinged with purple, 520°, table-knives and watch-springs.

3286. To Temper Drills

3286.     To Temper Drills. Heat the best steel to a cherry red, and hammer until nearly cold, forming the end into the requisite flattened shape, then heat it again to a cherry red, and plunge it into a lump of resin or into quicksilver. A solution of cyanide of potassium in rain water is sometimes used for the tempering plunge bath, but it is not as good as quicksilver or resin.

3287. To Temper Gravers

3287.     To Temper Gravers. These may be tempered in the same way as drills; or the red hot instrument may be pressed into a piece of lead, in which a hole about i an inch deep has been cut to receive the graver; the lead melting around and enclosing it will give it an excellent temper.

3288. To Temper Spiral Springs

3288.     To Temper Spiral Springs. Heat to a cherry red in a charcoal fire, and harden in oil. To temper, blaze off the oil 3 times, the same as for flat springs.

3289. To Temper Old Tiles

3289. To Temper Old Tiles. Grind out the cuttings on one side, until a bright surface is obtained; then damp the surface with a little oil, and lay the file on a piece of red-hot iron, bright side upwards. In about a minute the bright surface will begin to turn yellow; and when the yellow has deepened to about the color of straw, plunge in cold water.

3290. To Make Polished Steel Straw Color or Blue

3290.    To Make Polished Steel Straw Color or Blue. The surface of polished steel acquires a pale straw color at 460° Fahr., and a uniform deep blue at 580° Fahr.

3291. To Temper Mill Picks

3291.    To Temper Mill Picks. After working the steel carefully, prepare a bath of lead heated to the boiling point, which will be indicated by a slight agitation of the surface. In it place the end of the pick to the depth of l1/2 inches, until heated to the temperature of the lead, then plunge immediately in clear cold water. The temper will be just right, if the bath is at the temperature required. The principal requisities in making mill picks are: First, get good steel. Second, work it at a low heat; most blacksmiths injure steel by overheating. Third, heat for tempering without direct exposure to the fire. The lead bath acts merely as protection against the heat, which is almost always too great to temper well.