SHOP TOOLS.

11 I

cut without changing the knives, or injuring an unnecessarynumber of adjoining links.

Fig. 32 shows a general elevation of a Tweddell triplepunching and shearing machine, capable of punching lJ-inchholes in l^-inch plates, or shearing 1^-inch plates, or angle-irons 6| inches by 6| inches by •§ inch. The several tools forperforming these different operations are shown on fig. 32 atA, B, and 0. Fig. 33 is partly an elevation and partly a

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Fig. 33.

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vertical section of the punching-machine. A is the cylinder;B is the piston, which is prolonged by an eccentric stem C, towhich is attached the punch-holder D. The stem C, being