The Pattern Maker's Assistant; Embracing Lathe Work, Branch Work, Core Work, Sweep Work, and Practical Gear Contruction. the Preparation and Use of Tools Together with a Large Collection of Useful and Valuable Tables (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 edition. Excerpt: ...place battens below the box, and let in pieces of hard wood or metal above, as represented in Fig. 127, at G and H. CHAPTER VII. WHEEL AND PULLEY WORK. Our fourth example is a double flanged pulley, shown in section in Fig. 128; and our first consideration is, how it shall be molded. It evidently should he in the sand in the position shown in Pig. 129; but it will be observed that the sand is confined between two flanges, rendering it practically impossible to retract the pattern from the mold, if it is made in one piece. We say practically impossible, meaning that it cannot be done economically; for strictly speaking, an expert inolder with every requisite appliance, can mold almost anything, as any one will conclude who examines the various works of art in bronze which appear in art exhibitions and elsewhere. Our pattern must, for ease of molding, be made in two parts. If the disk (or spokes, if it be a spoke-wheel) be sufficiently thick to allow it, the division may be made at the center, that is to say, on the line A P, in Fig. 128. The operation of the molder may be understood from Fig. 129, three distinct beds of sand being necessary. It may be that a part of a flask is used for each bed, or it may be arranged as shown in Fig. 129, it being a matter of indifference to the pattern maker. In either case, however, draught should be allowed both inside and outside, that is to say, both the interior and exterior diameters of the pattern should be made smallest at the line of parting, the diameters increasing slightly as they approach the flanges. The hubs also should, in like manner, be slightly tapered. Inside sharp corners should be avoided; they should, in fact, always be rounded by cutting them out with a round-nosed tool. To construct this...