The die illustrated in [Fig. 9] is one of the most successful of the various types of casting-dies, and if properly made is an interesting piece of die work. The principal use of this particular style of die, called a slide die, is to cast parts like the one shown in [Fig. 10], which is a disk similar to the one which the last die described was to cast, except that it has raised letters at the edge and a hole in the center. It is obvious that the die last described, ([Fig. 8]), would not do for disks or other pieces having projections or depressions around their edges, as, for instance, printing or counting wheels with raised or sunken characters, or grooved pulleys. Briefly, this style of die is similar to the simple casting-die, except that slides are provided, to the required number, which form the edge of the casting. A die for a plain grooved pulley would require but two slides, while a die for a printing wheel with forty letters around its edge would necessitate forty slides, one for each of the letters. The die about to be described, shown in [Fig. 9], was made to cast a wheel with six raised letters.
Referring to [Fig. 9], D is the cast-iron box or frame, E, the lower die, and F the upper die. In making the lower die-half, the stock is first shaped to size and doweled to the blank for the upper die-half, and the holes for attaching to the frame are drilled. For the sake of clearness, these holes and screws are omitted from the illustration as are also the vents, since they have been fully explained. The lower die is next strapped to a faceplate, trued up, and bored out nearly to the diameter of the body of the piece to be cast, exclusive of the raised letters. The depth of this recess is equal to the thickness of the printing wheel plus 3/16 inch to allow for the cam ring G that is used to reciprocate the slides of the die. The cam ring is made large enough to cover the die-cavity as well as the slides that surround it, with an allowance of an inch or two for the cam slots H. The six slides I are made long enough to have good bearing surfaces. With the size of the cam ring determined, the die is next bored out to receive this cam ring and the last inch of the recess is carried down to the depth of the die cavity so as to make an ending space for the slots that the slides are to work in. The die is now taken from the faceplate and the slots for the slides laid out.
Fig. 9. Slide Die for Casting the Printing Wheel shown in [Fig. 10]
These slots may be milled or shaped, but milling is to be preferred. The next step is the making and fitting of the slides, which are of machine steel, having a good sliding fit in the slots. The six slides are fitted in position and left with the ends projecting into the die proper. The slots H are next profiled in the cam ring G, and the pins J that work in them are made and driven into the holes in the slides. With the slides and cam ring in place, the cam ring is rotated to bring all the slides to their inner position where they are held temporarily by means of the cam ring and temporary screws. The die-half with the slides thus clamped in the inner or closed position, is set up on the lathe faceplate and the die-cavity indicated up and bored out to the finish size, which operation also finishes the ends of the slides to the proper radius. The die may now be taken down and the slides removed to engrave the letters upon their concave ends. The engraving can be done in the best manner on a Gorton engraving machine, but if such a machine is not available they may be cut in by hand. Stamping should never be resorted to for putting in the letters, because the stock displacement would be so great that it would be impossible to refinish the surface to its original condition. Before fitting the cam ring, an opening must be milled in the die to allow the handle to be rotated the short distance necessary. After the cam ring has been fitted, it is held in by the four small straps K, attached by screws to the lower die-half at the corners.
Fig. 10. Printing Wheel cast in a Slide Die
The sprue cutter, which is not shown, is operated through the hole in the center of the piece and is, of course, round in this die. Its action is the same as was the one previously described, and the ejecting device is similar, with the exception that the brackets L that are attached to the ejector-pin plate M, are widely separated so as to make room for the sprue cutter that works through a hole in the plate M.
Die for Casting with Inserted Pieces
For making die-castings that are to have pieces of another metal inserted, it is necessary to have a die with provisions for receiving the metal blank and holding it firmly in position while the metal is being cast around it, and of course the piece must be held in such a manner that it can be easily withdrawn from the die with the finished casting.