Many patterns which at first may seem to be quite formidable, will, after a little study, resolve themselves into a few very simple parts, nearly all the work for which may be done in the lathe. Of this the T-pipe connection shown in Fig. 201 is a good illustration. A sectional view of the casting, threaded and having a pipe screwed into the right-hand end, is shown in Fig. 202.
The completed pattern for this casting is illustrated in Fig. 203, with its core prints a, a, and a, and must be parted, as shown in Fig. 204. The entire pattern may be mode at a single turning, as illustrated in Fig. 205. The preparation of the wood for this pattern is similar to that described for the pattern, Fig. 151, of the brass bearing.
Some device should always be used at the ends of stock glued in this manner to assist in making a firm joint. The metal corrugated fastener is best suited for most requirements. In some cases a flat head wood screw can be inserted at each end, Fig. 205, and the form of the pattern may require a wooden screw to be inserted near the center of the work to prevent it3 springing open at the center, due to the centrifugal forces at high revolutions.
Fig. 205. Pattern for Tee, Fig. 201, as Mounted in Lathe.
Fig. 206. Steel Center Plate.
Fig. 207. Steel Pinch Dog.
Fig. 208. Core Box for Tee.
Fig. 209. Elbow Pipe Fitting.
In mounting heavy split patterns in the lathe, a special metal dog should be provided, and one such as in Fig. 206 will be found to meet most requirements for this class of work. In using this dog, which is also the center on which the work revolves, cone lathe centers should be used, and a steel pin should be bolted to the lathe faceplate and inserted in a hole in the end of the stock to drive the work. Several holes can be countersunk in these metal lathe dogs when parts of the pattern are to be turned on several centers. The metal pinch dog, Fig. 207, is not adapted for lathe work, as it is liable to fly out when the work revolves, endangering the operator.
When the turning is completed, it is only necessary to cut a V-shaped opening into the two halves of e, into which the part f is to be fitted and glued. When the glue has set and is sufficiently dry, the joint may be further strengthened by nailing, or by inserting and screwing a thin metal connecting plate flush with the parting side of each half of the pattern. This, however, will be necessary only when patterns are large and heavy, or when unusual strength is required.
The core box for this pattern, as will be seen in Fig. 208, is the usual half box and is made by working out the box in one piece long enough to make the two parts a and b. The two parts are united by cutting a V-shaped opening in the part a and fitting 6 into it in the same way as described for the pattern. The whole is then glued and screwed to the board c, and the two triangular blocks d and d are glued in the angles to add strength to the completed box. In case the pattern is for a very small pipe, 1 1/2 inches or under, the part b may be abutted against the side of a, as shown by the dotted line, and the side of a at e cut away to the same curve as b, giving the same results as in the former method.
Fig. 211. Method of Turning Up Elbows.
The pattern for the 2-inch elbow, Fig. 209, is another illustration of how such work may be simplified, and time saved, by doing the greater part of the work in the lathe.
As these elbows are usually cast in large numbers, the patterns should be made double, as shown in Fig. 210.
Fig. 213. Coastruction of Core Box for Elbow Fitting.
To construct the double pattern, a ring is first turned like Fig. 211, a cross-section of which is a semicircle, as shown in the lower right-hand corner of the drawing. This ring is cut into quarters, and the four pieces e, e, e, and e make the quarter turns for the two halves of the double pattern.
The ends, including the core prints and connecting tenons, are turned in one piece, as shown in Fig. 212, the stock for which is prepared, with the inserted dowel pins all in position in the same manner as described for the T-pattern, Fig. 205. The quarters e, e, e, and e, Fig. 211, are clamped together two and two, and the ends carefully bored to receive the tenons which are then glued in position and further strengthened by a wooden screw.
In Fig. 213 the core box for this double pattern is shown, and, as will be seen, the most difficult part of the work can be done in the lathe. Fig. 214 shows two pieces jointed and clamped together which must be screwed to the faceplate of the lathe and turned out to make the two corners c and c. The three straight parts d, d, and d are worked out in one long piece and afterward cut to the required lengths, after which the five pieces are glued and screwed to the board a. The ends e and e are next put on and the required half-core box is complete.
Another reason why the pattern for pipe elbows should be made double is that otherwise the core prints would require to be made of great length in order to balance, sustain, and keep the heavy core in position; the tendency being to sag in the middle, or float on the molten iron, and thus make the upper side of the casting too thin, all of which is avoided in the double pattern.
Fig. 215. Return-Bend Pipe Fitting.
A pattern for the return bend, Fig. 215, may be built up and constructed in the same manner as described for the elbow; the semicircular returns, not only for the pattern, but also for the core box, being turned in the lathe, together with the ends and core prints for the pattern. As there will be no middle support for the core in this case, the core prints must be made as shown in the half pattern, Fig. 216, of sufficient length to balance the heavy semicircular core, and also to keep it in its true position in the mold. Screw Chuck. The small wood lathe chuck, a vertical section of which is shown in Fig. 217, will serve as a simple illustration of the long core print and balanced core. The casting must be counter-cored; that is, the cored opening must be enlarged at the forward end, adding to the size and weight of that end of the core, which, as will be seen, has no support except that afforded by the extra length of the core at the opposite end. The pattern for this chuck is shown in Fig. 218, and the core print must have a length at least twice as great as the depth of the hole in the chuck. The core box is shown in Fig. 219.
Fig. 218. Appearance of Pattern of Lathe Chuck.
When pipes or cylinders are of moderate size, with deep flanges for bolting together, Fig. 220, the flanges for the pattern are turned out of a separate disk, as shown in Fig. 221, and firmly glued and nailed on over the core prints and against the ends of the main body of the pattern; the core print being made of sufficient length to receive the flange. A recess is sometimes turned in the inside end of the core print to receive the inner edge of the flange, as shown in the diagram, Fig. 222; it can easily be seen that when the flange is fitted therein, it adds greatly to the strength of the joint.
Fig. 220. Flange Pipe Pattern.
Fig. 222. Diagram Showing Racord for Flanges in Pipe Pattern.
Fig. 223. Interchangeable Flanges on Pipe Pattern.
Flanges are often fastened to the pipe pattern by screws only, so that flanges of different diameter can be attached, Fig. 223.
The flanges should be made by gluing up three pieces and crossing the grain of the pieces so that the grain of each will run at right angles to that of the adjacent one. In gluing pieces together for thin disks, three pieces should always be used. Two thin pieces glued together will always warp.
A still better and stronger method of making large flanges is to cut out segments, fire or six for each course, and fit and glue up on a chuck and faceplate in the same way as described for the hand-wheel rim, Fig. 173. Two or three courses are used for each flange, which, after being turned to the required size and form, is sawed in two with a very thin saw, and each half fitted into place on the pattern.