[Illustration: Fig. 33. Section through a Die-casting Mold]
The next step consists of laying out the die, as shown in Fig. 36. This is done in the usual manner, by working on a coppered surface, using dividers, scales, and a center punch. When laying out the die, the necessary allowances are made for shrinkage and finish, these points having been planned before actual work on the die has been started. As in other phases of die-work, the machining operations are performed, as far as possible, before any hand-work is done. In Fig. 38 may be seen a die-maker turning the cavity in a part of the die-casting mold. The highest type of skilled workmanship is called for on this machine work, and as may be surmised from Fig. 38, where the die-maker is shown measuring the die with a vernier caliper, the measurements must be exact, for no grinding operations follow the machine work.
[Illustration: Fig. 34. First step in making the Mold--Grinding Surfaces of Blocks]
[Illustration: Fig. 35. A Milling Operation on a Die]
Figs. 35 and 39 show typical milling operations being performed on die-casting molds. In Fig. 39 the diemaker is shown indicating a pin in one corner of the mold cavity, preparatory to doing additional milling. The block is held in the usual manner by being clamped on the bed of the milling machine, and after it has been properly located under the cutter head, tools are substituted for the indicator and the milling of the cavity is completed. Fig. 35 shows one of the sections of the die-casting mold which is to be used in producing the casting shown at the right of the work. In this case the diemaker is milling the recess for the steel arbor which may be seen directly in the foreground. This will be fitted in place to provide for the forming of the hole in the side of the piece.
[Illustration: Fig. 36. Laying out One of the Mold Parts]
[Illustration: Fig. 37. Planning the Die-casting Mold]
[Illustration: Fig. 38. Turning out a Die-casting Mold]
[Illustration: Fig. 39. Indicating a Mold on the Milling Machine]
Fig. 40 illustrates several important points in the making of a die-casting mold. This illustration shows the ejector box with the lower half of the mold on it, the ejector plate being held against the under side of the die-plate by means of the pinion shaft. The operation being done is the drilling of the ejector-pin holes. Referring back to Fig. 32, which by the way shows the die here illustrated disassembled, the holes being drilled are those shown at _F_ for the reception of the pins _E_. The method employed is to drill the holes through the die and into the ejector plate, afterward reaming all holes to size and driving the pins into position in the ejector plate, while they are allowed to slide freely through the die-plate. We will now assume that the ejector box and plate have been completed and fitted, a pinion shaft for operating this plate also fitted, the lower and upper dies completed by the machining operations previously described, and all assembled. The final operation of the fitting of the pins is shown in Fig. 41 in which the die-maker may be seen filing off the ends of these pins so that when dropped to the lower position they will lie flush with the surface. If of uneven lengths, these pins will cause irregular spots in the casting. It now remains to describe the toggles used for operating the cores which form the holes through the three lugs in the casting. One of these toggles, of which there are three, is shown at _I_, in Fig. 31, and also in Fig. 32. These toggles consist of brackets which are attached to the die-plate, and levers which are fulcrumed at the ends of the brackets so that their operation works the core pins. It is necessary to remove these core pins after each casting has been made and position them before another casting can be produced.