“The flanges vary in shape; but as a rule small valves are provided with hexagons and large ones with round flanges suitable for bolting to similar flanges to make joints. For small valves, say up to 2 inches, the pattern is usually made with the hexagons cut out of the solid, but for sizes above that, they should be made in separate pieces, as shown in [Fig. 2798], and screwed to the pattern, so that in case of necessity they may be removed, and flanges substituted in their stead. In [Fig. 2799], we have a perspective view of the finished pattern; and [Fig. 2800] represents the pattern as prepared, ready to receive a flange or hexagon as may be required. A globe valve pattern should be made in halves, as shown in [Fig. 2801], the parting line of the two halves being denoted by a b. To make this pattern, we first prepare two pieces of wood so large that, when pegged together, the ball or body of the pattern can be turned out of them, and long enough not only to reach from p to p, in [Fig. 2799], but also to allow an excess by means of which the two pieces may be glued or otherwise fixed together. These two pieces we plane to an equal thickness, and then peg them to retain them in a fixed position, taking care, however, that the pegs do not occur where the screws to hold the flanges will require to be. We also place two pegs within a short distance of what will be the ends of the pattern when the excess in length referred to is turned off. We next prepare, in the same way, two more pieces, to form the two halves of the branch, shown at b, in [Fig. 2801], for which, however, one peg only will be necessary. These pieces must be somewhat wider than the size of the required hexagon across the corners, that is, supposing the hexagon is to be solid with the branch; otherwise we must make them a little wider than the diameter of the hub of the flange, or of the round part of the hexagonal pieces. Their lengths must be such as to afford a good portion to be let into the ball or body of the pattern (as shown by the dotted lines in [Fig. 2800]), which is necessary to give sufficient strength. The two pieces must be firmly fixed together, and then turned in the lathe.
Fig. 2800.
Fig. 2801.
Fig. 2802.