THE PACKING DEPARTMENT.--In Fig. 56 is shown the packing pots where the work is packed. These are of malleable cast iron, with an internal vertical flange around the hole _A_. This fits in a bell on the end of the cast-iron pipe _B_, which is luted in position with fireclay before the packing begins. At _C_ is shown a pot ready for packing. The crown gears average 10 to 12 in. in diameter and weigh about 11 lb. each. When placed in the pots, they surround the central tube, which allows the heat to circulate. Each pot contains five gears. Two complete scrap gears are in each furnace (_i.e._, gears which fail to pass machining inspection), and at the top of front pot are two or more short segments of scrap gear, used as test pieces to gage depth of case. [Illustration: FIG. 56.--Packing department and special pots.] After filling to the top with compound, the lid _D_ is luted on. Ten pots are then placed in a furnace. It will be noted that the pots to the right are numbered 1, 2, 3, 4, indicating the position they are to occupy in the furnace. The cast-iron ball shown at _E_ is small enough to drop through the pipe _B_, but will not pass through the hole _A_ in the bottom of the pot. It is used as a valve to plug the bottom of the pot to prevent the carburizing compound from dropping through when removing the carburized gears to the quenching bath. Without detracting from the high quality of the work, the metallurgist in this plant has succeeded in cutting out one entire operation and reducing the time in the hardening room by about 24 hr. Formerly, the work was carburized at about 1,700 deg.F. for 9 hr. The pots were then run out into the yard and allowed to cool slowly. When cool, the work was taken out of the pots, reheated and quenched at 1,600 deg.F. to refine the core. It was again reheated to 1,425 deg.F. and quenched to refine the case. Finally, it was drawn to the proper temper. SHORT METHOD OF TREATMENT.--In the new method, the packed pots are run into the case-hardening furnaces, which are heated to 1,600 deg.F. On the insertion of the cold pots, the temperature naturally falls. The amount of this fall is dependent upon a number of variables, but it averages nearly 500 deg.F. as shown in the pyrometer chart, Fig. 61. The work and furnace must be brought to 1,600 deg.F. Within 2-1/2 hr.; otherwise, a longer time will be necessary to obtain the desired depth of case. On this work, the depth of case required is designated in thousandths, and on crown gears, the depth in 0.028 in. Having brought the work to a temperature of 1,600 deg.F. the depth of case mentioned can be obtained in about 5-1/2 hr. by maintaining this temperature.