The Edison phonograph monthly (Mar 1903-Feb 1904)

EDISON PHONOGRAPH MONTHLY. 13 notched at the edge) cuts the half-dozen grooves around the inside of the cylinder; the third, or finishing tool, brings the narrowbearing surfaces left to the correct taper. These shaving tools operate very readily as the work is rotated at a very high speed, the material of course being a little softer than anything the average screw machine operator has ever had anything to do with. When the work is removed from the machine the wax contracts sufficiently in a moment to admit of the record being removed from the mold. And as fast as the records are finished inside they are placed on cast-iron shells, or hollow plugs, to prevent their being injured or becoming distorted in further cooling. They are next slipped, one at a time, on a taper arbor held in a machine spindle which is constantly in rotation, and the ends are here finished. After this operation each record is carefully inspected to see if it runs true and if it is free from flaws of all kinds. Passing this inspection, the record is packed in cotton. slipped into a cylindrical pasteboard box and packed ready for shipment. The molding of these records is without doubt one of the most delicate, accurate and interesting operations ever performed in a shop. Just consider for a moment the shallowness of the indentations in the surface of the master record ; the gold plating of the wax surface — indentations and all ; the preservation in the mold of each and every tiny swell corresponding to its hollow in the master ; the accurate reproduction on an endless number of records of every indentation in the surface of the original wax cylinder. The deepest of the impressions in the master are something less than one one-thousandth of an inch ; the shallowest are much less than this. The surface of the cylinder presents a wavy appearance not unlike that of a chattering lathe job, besprinkled as it is with these tin}' impressions. And yet all the circumferential grooves traced in the wax by the recording sapphire, and every shallow indentation — no matter how insignificant it may appear — are faithfully reproduced in the surface of the molded record. With this process a much harder preparation can be used and a more durable record made' than was possible under the old method of cutting each cylinder, and besides there is practically no wear upon the mold and the thousandth record molded in it is as clear and sharp and will reproduce the vibrations originally received by the master record as well as the first one cast. ©o=? Fig. 5. The Recorder. Fig. 7. The Reproducer. A sectional viewr of the recording device used is given in Fig. 5, a being the diaphragm of glass or mica about .005 inch thick and 1 3-16 inches in diameter; b the metal rim in which the diaphragm is held by means of a ring of wax, a thin rubber ring being placed, as shown, under the disk ; c a tube with spherical end matching a seat formed in the hub of b; d the body of the device bored to receive c and provided at the back with a neck to receive the tube at the end of the Phonograph horn. The part b is hinged at e, and at f is a stop pin limiting the downward movement of the diaphragm rim or weight. The recording point is shown at g; the holder h for the latter is cemented at the inner end to the diaphragm and at the outer end is attached to the rim b. The enlarged view at the top shows the sapphire point g more clearly. It has a body about .040 inch diameter cupped at the end, as indicated, to form a keen cutting edge and is reduced at the back to form a shank to fit a hole drilled in holder h. A good idea of the appearance — under a powerful microscope — of the surface of a record operated upon by this recorder is given in Fig. 6. The center lines of these rows of indentations are actually 0.01 inch apart as the lead screw rotating with the record arbor and feeding the recorder along the wax cylinder is cut 100 threads to the inch. The line traced on the record is therefore a thread of 0.01 inch pitch. Some very curious results are produced in the w-ax by the vibrating diaphragm and recorder ; the string of nearly round impressions shown to the right in this engraving illustrating the effect produced by a single "xvlophone note. A sectional view of the reproducer is shown in Fig. 7. Here i is the diaphragm built up of three disks of mica, and held bv a clamping ring between rubber rings in a shell or body j, the latter having the same general outline as the body of the recorder. At k is a hinged weight limited in its outward and downward movement by a stop-pin, and provided with a lug in _ which arm / carrying reproducer point m is pivoted. This arm is connected by a link with the diaphragm and causes the latter to vibrate as the reproducer follows the path formed by the recorder, the sound waves originally recorded being now reproduced. The sapphire m is showm enlarged above the section and it will be noticed that the head is button shaped, this form following readilv the deepest and shortest indentation m the record. These reproducing points, like those used in recording, are all made at the Orange shops, a large number of bench tools being used on this work alone. PICTURES AND SKETCHES OF THE ♦♦TALENT." An Illinios Dealer suggests that the Phonograph Monthly should contain each month a half tone cut and sketch of one or more of the artists who make Records for the Edison Phonograph. Similar suggestions have been made by others and we expect to do something in this line before long.