To successfully case-harden common cold rolled steel so that it will answer for the cutters of inserted reamers, etc., pack the cutters in granulated raw bone in a cast iron box with at least one-half inch layer of bone between the cutters and the sides of the box. Put on an iron cover and lute with fire-clay; heat in a gas furnace to almost a white heat for from two to five hours according to the size of the box. Then draw the box, open and dump quickly into a bath composed of the following: 1 quart of vitriol (sulphuric acid), 4 pecks common salt, 2 pounds saltpeter, 8 pounds alum, 1 pound prussiate potash, 1 pound cyanide potash and 40 gallons soft water.
S. Pittsburg, Pa. F. Wackermann.
Yellow prussiate of potash, by weight, 7 parts; bichromate of potash, 1 part; common salt, 8 parts; pulverize the crystals and mix thoroughly. Heat the piece to be hardened to a dark red and dip into the preparation or sprinkle it on the piece. Return to the fire and let it soak, then repeat several times according to the depth of hardened surface wanted. Finally plunge into water or oil. This may be used on tool steel, soft steel or iron.
Meriden, Conn. James P. Hayes.
There are several ways of obtaining the beautiful mottled effect on case-hardened articles, but one of the simplest and most effective methods is in use in the factory of the Thos. B. Jeffery Co., Kenosha, Wis. Here the usual cooling tank and screen for catching the work are in use, but in addition, an air pipe is run into the bottom of the tank in such a way that when the air is turned on the water is filled with air bubbles and is violently agitated. The result of these air bubbles striking the cyanide-coated articles during the cooling process, is some of the prettiest mottled work imaginable. E. V.
A simple and effective way to get a mottled effect in case-hardening with cyanide of potassium is as follows: Set an open pail or jar under a running hydrant, get the pieces good and hot (bright red) in a ladle of molten cyanide, then take out singly with tweezers and simply throw them into the water. The air bubbles rising through the water give the desired mottled effect. A still better process, if an air blast is at hand, is to connect a rubber hose in some manner to the bottom of the pail, so that a stream of air enters the water. This plan serves well where no special appliance is available for this class of work.
Chicago, Ill. Harry Ash.
One part sal-ammoniac and 3 parts prussiate of potash; or, 1 part prussiate of potash, 2 parts bone dust and 2 parts sal-ammoniac. ED. H. McClintock.
West Somerville, Mass.
To case-harden part of a piece to a line or in a spot cover the part or surface to be hardened with a moderately heavy coat of black japan enamel. I prefer this as it bakes on more closely than anything else. Clean the work thoroughly, then put on a heavy coat of copper and the work is now ready to be carbonized, and is packed in a pot in bone or leather in the usual manner. Heat long enough to give the required depth of "case." Then take out of the fire and cool down in the pot. When cold reheat and dip in oil or water. The copper blocks the absorption of carbon while the japan burns off and allows the carbon in the bone or leather to be absorbed by the iron.
E. W. Norton.
Mis 10 parts charred bone, 6 parts wood charcoal, 4 parts charred leather and 1 part of powdered cyanide potassium. Clean the work thoroughly, and do not handle with greasy hands. Pack the work with the mixture in a common gas pipe plugged at one end, and seal at the other with asbestos cement. Heat in a furnace to a dark cherry red and keep at that heat for about 4 or 5 hours. Dump in a tank with compressed air bubbling up through the bottom. If the colors are too gaudy leave out the cyanide. J. F. Sallows.
Grand Rapids, Mich.
The entire surface of the work, or that part which is to be hardened, should be coated with a moderately heavy coat of japan enamel, and then a medium heavy coat of copper should be applied to the remaining portion of the work. In applying the copper, care should be taken not to disturb the japan. After the copper is applied, the piece is ready to be carbonized. It should be packed, and heated to a bright red, and held at this heat long enough for the requirements of the work. Then the box or case, containing the pieces to be case-hardened, are taken out of the fire and the work is permitted to cool in the box. When cool, the work is taken out and reheated in the open fire, and dipped in oil or water. The copper prevents the absorption of the carbon, while the japan enamel burns off and allows the carbon to take effect. E. S. Wheeler.