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To Temper Small Steel Articles

The tempering of small drills, for drilling holes in arbors, staffs, etc., which we find are very hard and difficult to perforate, may be effected in the following manner: After having filed the drill to its proper size (being careful not to flatten the cutting face), you then warm it moderately, not allowing it to become red, and run it into borax. The drill is thus coated over with a crust of borax and secluded from the air. Now it may be hardened by heating it only cherry red; after this it is inserted into a piece of borax, or what is better still, plunged into mercury; taking care not to breathe the mercury fumes. Drills prepared in this way, without being brittle, will become exceedingly hard and the watchmaker will be enabled to drill articles which could not otherwise be perforated with a drill. Do not use broken broaches to make your drills, as the steel in them is often burned, rendering the metal unfit for use in small tools. In order to make the quality of your drill a certainty, always take a new piece of round steel for the purpose.

To Harden Steel in Petroleum. According to B. Morgossy, the articles to be hardened are first heated in a charcoal fire, and, after thoroughly rubbing with ordinary washing soap, heated to a cherry red. In this condition they are plunged into petroleum; ignition of the petroleum need not be feared if no flame is near at hand. Articles hardened by this method show no crack, do not warp if plunged endwise, and after hardening remain nearly white, so they can be blued without further preparation.