Of Copying By Punching





133. This mode of copying consists in driving a steel punch

through the substance to be cut, either by a blow or by pressure.

In some cases the object is to copy the aperture, and the

substance separated from the plate is rejected; in other cases

the small pieces cut out are the objects of the workman's labour.



134. Punching iron plate for boilers. The steel punch used

for this purpose is from three-eighths to three-quarters of an

inch in diameter, and drives out a circular disk from a plate of

iron from one-quarter to five eighths of an inch thick.



135. Punching tinned iron. The ornamental patterns of open

work which decorate the tinned and japanned wares in general use,

are rarely punched by the workman who makes them. In London the

art of punching out these patterns in screw-presses is carried on

as a separate trade; and large quantities of sheet tin are thus

perforated for cullenders, wine-strainers, borders of waiters,

and other similar purposes. The perfection and the precision to

which the art has been carried are remarkable. Sheets of copper,

too, are punched with small holes about the hundredth of an inch

in diameter, in such multitudes that more of the sheet metal is

removed than remains behind; and plates of tin have been

perforated with above three thousand holes in each square inch.



136. The inlaid plates of brass and rosewood, called buhl

work, which ornament our furniture, are, in some instances,

formed by punching; but in this case, both the parts cut out, and

those which remain, are in many cases employed. In the remaining

illustrations of the art of copying by punching, the part made

use of is that which is punched out.



137. Cards for guns. The substitution of a circular disk of

thin card instead of paper, for retaining in its place the charge

of a fowling-piece, is attended with considerable advantage. It

would, however, be of little avail, unless an easy method was

contrived of producing an unlimited number of cards, each exactly

fitting the bore of the barrel. The small steel tool used for

this purpose cuts out innumerable circles similar to its cutting

end, each of which precisely fills the barrel for which it was

designed.



138. Ornaments of gilt paper. The golden stars, leaves, and

other devices, sold in shops for the purpose of ornamenting

articles made of paper and pasteboard, and other fancy works, are

cut by punches of various forms out of sheets of gilt paper.



139. Steel chains. The chain used in connecting the

mainspring and fusee in watches and clocks, is composed of small

pieces of sheet steel, and it is of great importance that each of

these pieces should be of exactly the same size. The links are of

two sorts; one of them consisting of a single oblong piece of

steel with two holes in it, and the other formed by connecting

two of the same pieces of steel, placed parallel to each other,

and at a small distance apart, by two rivets. The two kinds of

links occur alternately in the chain: each end of the single

pieces being placed between the ends of two others, and connected

with them by a rivet passing through all three. If the rivet

holes in the pieces for the double links are not precisely at

equal distances, the chain will not be straight, and will,

consequently, be unfit for its purpose.





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