Methods of machine shop work; for apprentices and students in technical and trade schools

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. 1914 Excerpt: ...because of the flexibility of the calipers, this increased effort is so small that, to all but the highly skilled, it is imperceptible. This shows at once the function of stiffness in gages which become more sensitive as they are made stiffer with, however, a limitation which grows out of the fact that increased stiffness is necessarily accompanied by increased weight and this increased weight, if carried too far, dulls the sense of touch. Were the snap gage of Fig. 52 to weigh ten pounds, for example, the increased effort necessary to force it over the larger plug would be lost in the weight of the gage and the hand would not feel it. This consideration has immediate application to large gages. Were the weights of large gages made proportional to their sizes in order to maintain the stiffness, the effect would be to destroy the very object of this construction by reason of its effect in dulling the sense of touch and, moreover, such gages would be clumsy and unwieldy. It is, consequently, impracticable to make large gages of the same relative stiffness as small ones and this compels us, when using large gages, to resort to expedients. Because of their comparative flexibility large gages are subject to distortion from the effect of their own weight and, if satisfactory measurements are to be obtained, it is necessary to find means by which this distortion may be neutralized. Figs. 93 and 94 show such an expedient used at the works of the Westinghouse Machine Company. The piece of work to be gaged--shown beyond the operator and in the lathe--is a thirty-nine inch crank shaft, in front of which is a micrometer caliper of suitable size. In order to combine lightness with stiffness as far as possible, the frame of the caliper is made of aluminum alloy. At its u...