F. W. PUTNAM

The next pattern to be described is for a hollow tray. Large trays of the same style are frequently used on machines for holding tools and are then known as tool trays. Fig. 55 shows the pattern which is to be made with a vertical core. It will be noticed that the tray is hollow or recessed; the green sand core which forms this, projecting downwards from the cope.

The hub A, Fig. 55, is turned, together with the core prints, from one block of wood, as shown in Fig. 56. The plate, or bottom of the tray, is made from a piece of wood 3/16 in. thick, as shown in Fig. 57. A hole £ in. in diameter is bored through the center of this plate to receive the two parts of the hub, which are made with shoulders 3/8 in. in diameter to fit this hole. The shoul-der is clearly shown at B, Fig. 56, the block, after being turned, being cut in two pieces at D with a back saw. The sides of the tray are shown in Fig. 58.

It will be noticed that the sides are bevelled 1/16 in. to allow the green sand core to be removed easily from the mold. These pieces are so small that care must be taken in planing them. It will probably be found advisable to use two pieces of stock about 8 in. long, each piece being later cut up for one long and one short side. These sides are to be glued and nailed to the plate, or base piece. The corners are mitred; the ends of the side pieces being, of course, cut off at 45°. The two parts of the hub are fastened to the plate simply with glue. This will prove amply sufficient, if the shouldered ends fit tightly in the center of the plate.

Fig. 55.

Fig. 56.

Fig.60.

Fig. 55 should be carefully studied before the hubs are glued together. The tapered part of the core print C, Fig. 56, is to come on the top side of the plate, as shown in Fig. 55. The arrow in Fig. 55 shows the direction in which the pattern is to be withdrawn from the sand. This draft should not be made until the sides have been finally fastened to the plate. The hub and bottom core print being round, may be made without draft, if they are sand-papered to a very smooth surface, but care must be taken that there is no back draft at these points.

Fig. 57.

The next pattern brings in a new principle; that of using loose pieces with the pattern. Fig. 59 shows the casting of a small V way, as it is called. These V ways are in very common use on machines. Sometimes the tail stock of a wood turning lathe or machine lathe has a V way for a base piece, being similar to the one shown in Fig. 59. This V way slides along a dove-tailed track and has the advantage over the ordinary tail stock of never raising from the shears.

Fig. 58.

Fig. 60 shows three views of the pattern for this casting. The pattern is made up of seven parts; A, Fig, 60, is the base piece ; B is the end piece, which is fastened to the top surface of A ; C is the loose piece, made separate from the rest of the pattern, and used to form an angle of 60° with the top surface of the base. The stock should be taken wide enough to make both B and C, and should be planed to the required thickness, § in. The bevel of 60° is planed on one edge and carefully tested with the T-bevel.

Fig. 59

The block which should be long enough to make both sets of pieces, B and C; B can then be readily planed to the required width, 3/4 in. The edge of the piece (7, left rough by the saw cut, must also be planed so as to leave the stock 1/2 in. in width. Having sharpened the planer blade, next clamp C in the vise very carefully so as not to crush the block and plane down this rough edge. If a good vise with a perfectly smooth jaw is not available the piece C may be drawn over the bottom surface of the plane by hand. 0 must fit tightly against B, so that a close joint may be made at D, Fig. 60. These loose pieces are necessary because the parts C, Fig. 60, overhang, so that the pattern cannot be removed from the sand in any direction. In cases like this the over-hanging parts are fastened loosely to the main part of the pattern by wires or wooden pins.

After the pattern has been rammed up in the nowell, the base part A, Fig 60, is moved in the direction of the arrow, the parts C being still left in their positions in the sand. These are next carefully moved towards the center of the opening and lifted out. It is evident that the loose pieces must be easily separated from the main body of the pattern and should, therefore, be fastened by pins, so that they can be readily removed.

Fig. 60 shows the holes that are to be bored to receive the wood pins. These pins are 3/16 in. in diameter. They may be made slightly smaller, but if this is done care must be taken that the pins do not twist off when the pattern is molded. No draft should be made on the pattern until all parts are complete. Instead of tapering the loose pieces slightly for draft, they may be squared off 3/64 in. less in length than the width of the base piece.