The regulator bar should be hardened by being placed in a folded piece of sheet iron and heated red hot, and thrown into cold water. The regulator bar A A’ is about 3” long; and for holding it for hardening, cut a piece of thin sheet iron 21/2” by 31/4” and fold it through the middle lengthwise, as indicated by the dotted line g, Fig. 44. The sheet iron when folded will appear as shown at Fig. 45. A piece of flat sheet metal of the same thickness as the regulator bar should be placed between the iron leaves I I, and the leaves beaten down with a hammer, that the iron may serve as a support for the regulator during heating and hardening. A paste made of castile soap and water applied to the regulator bar in the iron envelope will protect it from oxidizing much during the heating. The portions of the regulator bar marked h are intended to be rounded, while the parts marked m are intended to be dead flat. The rounding is carefully done, first with a file and finished with emery paper. The outer edge of the loop A’’ is a little rounded, also the inner edge next the cap C. This will be understood by inspecting Fig. 46, where we show a magnified vertical section of the regulator on line l, Fig. 40. The curvature should embrace that portion of A’’ between the radial lines o o’, and should, on the model, not measure more than 1/40”. It will be seen that the curved surface of the regulator is sunk so it meets only the vertical edge of the loop A’’. For the average workman, polishing the flat parts m is the most difficult to do, and for this reason we will give entire details. It is to be expected that the regulator bar will spring a little in hardening, but if only a little we need pay no attention to it.
[Illustration: Fig. 44]
[Illustration: Fig. 45]
[Illustration: Fig. 46]
Polishing a regulator bar for a large model, such as we are building, is only a heavy job of flat steel work, a little larger but no more difficult than to polish a regulator for a sixteen-size watch. We would ask permission here to say that really nice flat steel work is something which only a comparatively few workmen can do, and, still, the process is quite simple and the accessories few and inexpensive. First, ground-glass slab 6” by 6” by 1/4”; second, flat zinc piece 31/4” by 31/4” by 1/4”; third, a piece of thick sheet brass 3” by 2” by 1/8”; and a bottle of Vienna lime. The glass slab is only a piece of plate glass cut to the size given above. The zinc slab is pure zinc planed dead flat, and the glass ground to a dead surface with another piece of plate glass and some medium fine emery and water, the whole surface being gone over with emery and water until completely depolished. The regulator bar, after careful filing and dressing up on the edges with an oilstone slip or a narrow emery buff, is finished as previously described. We would add to the details already given a few words on polishing the edges.