To harden drills for cutting glass, dissolve zinc in muriatic acid to saturation, then reduce the solution by adding an equal volume of water. Dip and use without tempering. E. W Norton.
To successfully harden dies for fine work, such as are used by jewelers and others, be careful to have the surface free from all grease or oil, pack face downward in a mixture of equal parts of finely powdered hardwood charcoal and charred bone. Dip in salt water and draw temper to 450 degrees F. Hardener.
It is possible to prevent the formation of any scale in the impression of fine Jewelers' dies and the like, and retain the finished brilliancy of surface, by applying a mixture of powdered ivory black and 6perm oil, mixed to the consistency of paste. It is only necessary to apply a thin coat. Hardener.
To remove excess oil from parts that have been hardened in oil, place the articles in a small tank of gasoline, which, when exposed to the air, will dry off immediately, allowing the part to be polished and tempered without the confusing and unsightly marks of burnt oil.
New York. H. J. Bachmann.
The following oil bath mixture gives excellent results for hardening spiral springs: Two gallons best whale oil, 2 pounds Russian tallow, and ½ pound rosin. Boil the tallow and the rosin together until dissolved; add the whale oil and stir up well, and then it is ready for use.
Birmingham, Eng. W. R. Bowers.
To prevent molten lead from sticking to the pot or the tools heated in it, cover the surface with a mixture of powdered charcoal, 1 quart; salt, ½ pint; yellow pruss-iate of potash, 1 gill; and cyanide of potassium a lump the size of a walnut.
If a punch, reamer or other tool is to be hardened, and the color resulting from that process is undesirable, it may be removed by the following simple method. After the part is hardened, dip it into a glass filled with muriatic acid and allow it to remain for five seconds; then plunge it into a pail of water. In this way the polish of the steel will return and then temper will not be affected. This method is much quicker than obtaining a polish by the use of emery cloth. John C. Monrad.
Buffalo, N. Y.
I would submit the following formula as an excellent compound for hardening and tempering steel: To 10 gallons of soft water, add 5 teacups of salt, 6 ounces saltpeter, 12 teaspoonfuls of powdered alum, and 1 teaspoonful corrosive sublimate. We have tempered flat cutters, Acme and U. S. standard taps, counterbores, reamers, etc., to our entire satisfaction, without drawing the temper in any of them.
Columbus, O. H. S. Hindman.