. Railway mechanical engineer . manner. This will tendto eliminate the scale on the surface and the warping of thetool. A mixture of two-thirds salt and one-third cyanide ofpotassium, heated to a red heat for one hour and allowed tocool and harden and then mixed in the lead bath, is a goodmethod to prevent the lead from sticking to the threads andsmall projections of the tool. The top of the lead pot shouldbe covered with bone black. The following method is used for hardening high speedsteel threading dies, taps and other delicate high speed steeltools: The tools are first packed in a cast iro
. Railway mechanical engineer . manner. This will tendto eliminate the scale on the surface and the warping of thetool. A mixture of two-thirds salt and one-third cyanide ofpotassium, heated to a red heat for one hour and allowed tocool and harden and then mixed in the lead bath, is a goodmethod to prevent the lead from sticking to the threads andsmall projections of the tool. The top of the lead pot shouldbe covered with bone black. The following method is used for hardening high speedsteel threading dies, taps and other delicate high speed steeltools: The tools are first packed in a cast iron box or pipewith charcoal, care being taken that none of the articles touchthe side of the box. The box is then covered and heated tofrom 1,950 to 2,050 deg. for from two-and-a-half to threehours, according to the size of the box. The box is thenallowed to remain in the furnace. On opening the box thedies are removed individually and quenched in oil. All high President,Association 172 RAILWAY MECHANICAL ENGINEER Vol. 90, No. 9. C. A. Shaffer, 1st Vlce-Pres.,Tool Foremens Association speed steel tools not hardened by the pack method should firstbe preheated to about 1,500 deg. and then placed in a furnaceof higher temperature and brought up to the desired benefit derived from this treatment is that a more last-ing cutting edge is obtained due to the fact that the surface ofthe tool has not been exposed to a high heat for any materiallength of time. We have found that vanadium steels arebest suited for concussion tools. In carbon and vanadiumSteels a higher temperature than is used for hardening shouldbe used for most high speedsteels 1,500 deg. F. isabout the proper heatfor annealing. O nbringing the tools upto this temperature thefurnace should besealed, the heat turnedoff and the furnai eallowed to cool grad-ually, and the contentsshould not be with-drawn until they arecold. Owen D. Kinsey,formerly of the IllinoisCentral: To obtainmaximum efficiency ofto
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