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Show ' mumt " 1 1 1 "' ' 11 h.dltd by U. DoukIhh Wanlrup, Kdltor of Radio Merchundluino Here Is a simple vernier arrangement arrange-ment for variometers and condensers which will he found very convenient In tuning for C.W. Fig. 1 shows the ruliber knob and the binding post from which the vernier Is made. Almost any type or size of rubber knob may be used. The dimensions dimen-sions shown, of course, will require to be changed accordingly. The knob used measured one-half Inch In diameter diame-ter and one-half Inch deep, with a knurled rim three-quarters of an Inch in diameter. To adapt this binding post face off the one-half inch length to one-quarter inch, and bevel the length to an angle of 45 degrees. This can be conveniently done by screwing the knob on a threaded rod which Is put Into a collet and turned in a lathe. The threaded rod Is an 8-32 machine screw with the head cut oft. An 8-M2 round-head machine screw, a one-half Inch spring to pass over the machine screw and a small brass washer complete com-plete I be vernier. A bole Is drilled through the panel slightly below the Pi 1 .., dial of tbe variometer to pass the 8-32 machine screw. The screw is inserted through this hole and the spring washer slipped over it, and, lastly, the tapered rubber knob is screwed on. It is preferable to use a machine screw which is threaded only at the end on which the knob is screwed as a machine screw entirely threaded tends to catch in the hole when the vernier is manipulated. To operate the vernier a slight pressure is applied ap-plied while turning, which permits the tapered periphery of the vernier to engage en-gage with the rim of the dial, enabling a micrometer adjustment. |