Nikola Tesla Books
102 HIGH FREQUENCY APPARATUS to keep the necessary tension on the movement. The builder will be required to do some simple pattern making, but this need not alarm him. It is to be deplored that the average amateur has such a pronounced antipathy to anything in the nature of a pattern or a casting, whereas the latter is frequently the simplest way out of a given difficulty. The pattern for the electrode castings is illustrated in Fig. 2. It is turned out of a block of whitewood secured to the faceplate of the lathe, care being taken to leave the extra stock on the edge to provide the necessary draft. When the pattern has been turned out it should be sent to the nearest foundry for a pair of copper castings as nearly pure as the shop can supply. Given the copper castings the worker grips No. 1 in the lathe chuck by the outer edge with the sparking face of the casting next to the face of the chuck. A good chip is taken off the projecting portion to remove the scale and the face finished with a light cut. The centering tool is then brought up in the tailstock and the casting centered. A 3 drill is next run very carefully through the casting and this is followed with the 1-18 tap, which should be started with the tailstock center against it to insure accuracy. The hole threaded, the casting may be removed from the chuck and laid aside temporarily while exactly the same operations are done on the No. 2 casting. This latter must also have holes drilled to take the pins 7 after the casting has been removed from the lathe. So far the worker will have faced off the hubs of the castings and provided the tapped holes for the spindles, and this in a manner that insures that the spindle will be truly at right angles to the plane of the hub. The next operation is to prepare the spindles for facing off the sparking surfaces of the castings. The spindle 3 is first prepared. It is to be used as an arbor upon which
