The Edison phonograph monthly (Mar 1903-Feb 1904)

12 EDISON PHONGRAPH MONHTLY. Fig. 2. Apparatus for Plating Records. The conductors are hooked at the top, and on these hooks are suspended two strips of gold leaf k k. The magnet / is arranged to be revolved by means of the pulleys shown, and armature d and the wax cylinder turn with it. An arc being established between the electrodes suspended on the conductors, the gold is vaporized and — as the wax record rotates in the vacuum — is deposited in an infinitesimally thin coating upon the surface of the cylinder. The master record now having received its plating of gold is electro copper plated, about four days being required to secure the desired thickness of copper — nearly 1-16 inch. This copper shell, with the master still within it, is then turned off smooth and straight and fitted into a brass shell, which forms really the body of the mold. A section through the mold would now appear something like Fig. 3, m being the master, n the copper shell (between which the wax surface is the minutely thin coating of gold), and 0 the brass shell in Fig. 3.— Section of Mould. Fig. 6.— Appearance of Record under Microscope. which is fitted the copper sleeve. The wax is removed from the mold by placing the latter for a few moments in a temperature slightly lower than that of the work-room, the contraction of the wax releasing it from the metal. The inside of the mold, which is now gold lined, is thoroughly cleaned by washing with benzine, and the mold is ready for business. For holding the wax preparation from which the records are formed, a number of long tanks, subdivided into nearly square compartments and heated by gas, are provided. The melted wax in these tanks is dark brown in color — in fact, nearly black. In molding the record the mold is lowered into the hot wax by means of an arrangement shown roughly in Fig. 4. In this sketch p is the mold, q a cap Fig. 4. Molding a Record. placed over the top of the latter, and r a can in which the mold is placed and held, as indicated, in a vertical position. The can is carried in a frame s, which may be moved up and down on uprights t by means of the wire bail u. The can is lowered into the tank until the top of the mold is below the surface of the wax v, the latter entering the mold through the large opening in the bottom of the can. The wax as it passes up into the mold solidifies on coming into contact with the metal and a hollow cylinder of wax is thus formed, the thickness of the cylinder wall depending of course upon the length of time the mold is immersed and also upon the temperature of the liquid. After remaining in the wax for a minute or so the can is lifted, the cap taken off and the mold removed. The wax adhering to the bottom of the latter is removed by a knife and the mold is then slipped into a special chuck in a machine of the monitor type. Inside shaving tools held in the turret of this machine are then run into the wax cylinder to finish the bore. These tools are made of steel tubing cut away to the center for a length sufficient to reach through the cylinder and ground to a sharp edge. The tools are somewhat smaller than the rough hole left in the work, and after being run in to the right distance they are brought over against the wax wall by a lever which serves to move the turret laterally on its carriage. Three tools are required to finish the bore ; the first roughs out a plain taper hole; the second (which is