Hardening, tempering, annealing and forging of steel; a treatise on the practical treatment and working of high and low grade steel .. . re gall and nerve, takeschances and either comes out on top or manages to cover up hismistakes. Beware of such men; they are responsible for morebad work in the shop than any others. First and foremost, the effect of annealing on steel which is 96 HARDENING, TEMPERING AND ANNEALING. desired to be afterward hardened must be understood and appre-ciated. First, the anneahng process softens and allows the steelto be worked into shape with ease. Second, it removes
Hardening, tempering, annealing and forging of steel; a treatise on the practical treatment and working of high and low grade steel .. . re gall and nerve, takeschances and either comes out on top or manages to cover up hismistakes. Beware of such men; they are responsible for morebad work in the shop than any others. First and foremost, the effect of annealing on steel which is 96 HARDENING, TEMPERING AND ANNEALING. desired to be afterward hardened must be understood and appre-ciated. First, the anneahng process softens and allows the steelto be worked into shape with ease. Second, it removes all strainssustained in the manufacture, such as rolling, hammering andforging. Thus experience teaches that it is necessary to annealany odd shaped piece after all the surface scale has been removedand the piece roughed down. Different Quenching Baths—Their Effect on Steel. As, next to proper heating, more depends upon the quenching than anything else, it follovv^s that the effects of the use of the various kinds of baths are required to be understood. The most generally used bath is usually cold water, though not infrequently. FIG. 58.—SCREW MACHINE SPRING THREADING DIES. -salt is added or a strong brine is used. The following will befound to answer well for the work mentioned: For very thin anddelicate parts, an oil bath should be used for quenching. Forsmall parts which are required to be very hard, a solution composedof about a pound of citric acid crystals dissolved in a gallon ofwater will do. For hardening springs, sperm oil; and for cuttingtools, raw linseed oil will prove excellent. Boiled water has often proved the only bath to give goodresults in a large variety of work, the parts requiring hardeningbeing heated in a closed box or tube to a low red heat and thenquenched. Sometimes the water should be boiling, at others quitehot, and then again lukewarm. Experience will teach the operator THE HARDENING OF STEEL. 97 ?which is the best for special work. If a cutti
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