American Blacksmithing, toolsmiths' and steelworkers' manual . e cases the thin or extended part will crack off ina solid ring. To stop a milling cutter of this kind fromcracking, fill the hollow in the end, as in Figure 49,with asbestos, being careful not to cover any of thecutting edges of the teeth and hold the asbestos inplace by the use of fine wire, while hardening. Thereason the tool will not crack is, when quenching to 104 THE TWENTIETH CENTURY harden only the teeth side comes in contact with thewater which hardens, while the other side is kept softas the asbestos keeps the water from
American Blacksmithing, toolsmiths' and steelworkers' manual . e cases the thin or extended part will crack off ina solid ring. To stop a milling cutter of this kind fromcracking, fill the hollow in the end, as in Figure 49,with asbestos, being careful not to cover any of thecutting edges of the teeth and hold the asbestos inplace by the use of fine wire, while hardening. Thereason the tool will not crack is, when quenching to 104 THE TWENTIETH CENTURY harden only the teeth side comes in contact with thewater which hardens, while the other side is kept softas the asbestos keeps the water from coming in contactwith the hot steel. Another example: Take a piece of steel 3 inches longand 1 inch thick, now an inch on each end is to behardened, while the remaining inch in the center is tobe kept soft, and to accomplish this process, wrap thecenter well with asbestos, keeping it in place by wind-ing some fine wire around it, or instead of using asbes-tos, wrap the steel around with clay, keeping it inplace by the use of a thin piece of sheet metal wound. Fig. 49. The angle end milling cutter. around it, then heat to harden and the results will beas formerly explained. Hardening Hollow Tools. When hardening milling cutters as a, Figure 48,ispring threading dies or any similar tool, alwaysquench them from a vertical or upright position, whichwill allow the steam and water to come up through thetool and cause the steel to be hardened more the tool be quenched from a horizontal position TOOLSMITH AND STEELWORKER 105 it will be impossible for the steam to escape, and whichwill keep the water from coming in contact with thehot steel. Thus when the water is held back by thesteam there is a tendency for soft spots in the tool. As a rule steel workers never pay any attention tothe steam when hardening, which is a great mistake, asmany tools are partially if not altogether spoiled (moreespecially if the tools are of a delicate nature) by thegreat amount of steam which
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