On the Economy of Machinery and Manufactures - Charles Babbage (interesting books to read in english .TXT) 📗

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.

 

Copying with elongation

 

140. In this species of copying there exists but little

resemblance between the copy and the original. It is the

cross-section only of the thing produced which is similar to the

tool through which it passes. When the substances to be operated

upon are hard, they must frequently pass in succession through

several holes, and it is in some cases necessary to anneal them

at intervals.

 

141. Wire drawing. The metal to be converted into wire is

made of a cylindrical form, and drawn forcibly through circular

holes in plates of steel: at each passage it becomes smaller.

and, when finished, its section at any point is a precise copy of

the last hole through which it passed. Upon the larger kinds of

wire, fine lines may sometimes be traced, running longitudinally.

these arise from slight imperfections in the holes of the

draw-plates. For many purposes of the arts, wire, the section of

which is square or half round, is required: the same method of

making it is pursued, except that the holes through which it is

drawn are in such cases themselves square, or half-round, or of

whatever other form the wire is required to be. A species of wire

is made, the section of which resembles a star with from six to

twelve rays; this is called pinion wire, and is used by the

clockmakers. They file away all the rays from a short piece,

except from about half an inch near one end: this becomes a

pinion for a clock; and the leaves or teeth are already burnished

and finished, from having passed through the draw-plate.

 

142. Tube drawing. The art of forming tubes of uniform

diameter is nearly similar in its mode of execution to wire

drawing. The sheet brass is bent round and soldered so as to form

a hollow cylinder; and if the diameter outside is that which is

required to be uniform, it is drawn through a succession of

holes, as in wire drawing: If the inside diameter is to be

uniform, a succession of steel cylinders, called triblets, are

drawn through the brass tube. In making tubes for telescopes, it

is necessary that both the inside and outside should be uniform.

A steel triblet, therefore, is first passed into the tube, which

is then drawn through a succession of holes, until the outside

diameter is reduced to the required size. The metal of which the

tube is formed is condensed between these holes and the steel

cylinder within; and when the latter is withdrawn the internal

surface appears polished. The brass tube is considerably extended

by this process, sometimes even to double its first length.

 

143. Leaden pipes. Leaden pipes for the conveyance of water

were formerly made by casting; but it has been found that they

can be made both cheaper and better by drawing them through holes

in the manner last described. A cylinder of lead, of five or six

inches in diameter and about two feet long, is cast with a small

hole through its axis, and an iron triblet of about fifteen feet

in length is forced into the hole. It is then drawn through a

series of holes, until the lead is extended upon the triblet from

one end to the other, and is of the proper thickness in

proportion to the size of the pipe.

 

144. Iron rolling. When cylinders of iron of greater

thickness than wire are required, they are formed by passing

wrought iron between rollers, each of which has sunk in it a

semi-cylindrical groove; and as such rollers rarely touch

accurately, a longitudinal line will usually be observed in the

cylinders so manufactured. Bar iron is thus shaped into all the

various forms of round, square, half-round, oval, etc. in which

it occurs in commerce. A particular species of moulding is thus

made, which resembles, in its section, that part of the frame of

a window which separates two adjacent panes of glass. Being much

stronger than wood, it can be considerably reduced in thickness,

and consequently offers less obstruction to the light; it is much

used for skylights.

 

145. It is sometimes required that the iron thus produced

should not be of uniform thickness throughout. This is the case

in bars for railroads, where greater depth is required towards

the middle of the rail which is at the greatest distance from the

supports. This form is produced by cutting the groove in the

rollers deeper at those parts where additional strength is

required, so that the hollow which surrounds the roller would, if

it could be unwound, be a mould of the shape the iron is intended

to fit.

 

146. Vermicelli. The various forms into which this paste is

made are given by forcing it through holes in tin plate. It

passes through them, and appears on the other side in long

strings. The cook makes use of the same method in preparing

butter and ornamental pastry for the table, and the confectioner

in forming cylindrical lozenges of various composition.

 

Of copying with altered dimensions

 

147. Of the pentagraph. This mode of copying is chiefly used

for drawings or maps: the instrument is simple; and, although

usually employed in reducing, is capable of enlarging the size of

the copy. An automaton figure, exhibited in London a short time

since, which drew profiles of its visitors, was regulated by a

mechanism on this principle. A small aperture in the wall,

opposite the seat in which the person is placed whose profile is

taken, conceals a camera lucida, which is placed in an adjoining

apartment: and an assistant, by moving a point, connected by a

pentagraph with the hand of the automaton, over the outline of

the head, causes the figure to trace a corresponding profile.

 

148. By turning. The art of turning might perhaps itself be

classed amongst the arts of copying. A steel axis, called a

mandril, having a pulley attached to the middle of it, is

supported at one end either by a conical point, or by a

cylindrical collar, and at the other end by another collar,

through which it passes. The extremity which projects beyond this

last collar is formed into a screw, by which various instruments,

called chucks, can be attached to it. These chucks are intended

to hold the various materials to be submitted to the operation of

turning, and have a great variety of forms. The mandril with the

chuck is made to revolve by a strap which passes over the pulley

that is attached to it, and likewise over a larger wheel moved

either by the foot, or by its connection with steam or water

power. All work which is executed on a mandril partakes in some

measure of the irregularities in the form of that mandril; and

the perfect circularity of section which ought to exist in every

part of the work, can only be ensured by an equal accuracy in the

mandril and its collar.

 

149. Rose engine turning. This elegant art depends in a great

measure on copying. Circular plates of metal called rosettes,

having various indentations on the surfaces and edges, are fixed

on the mandril, which admits of a movement either end-wise or

laterally: a fixed obstacle called the ‘touch’, against which the

rosettes are pressed by a spring, obliges the mandril to follow

their indentations, and thus causes the cutting tool to trace out

the same pattern on the work. The distance of the cutting tool

from the centre being usually less than the radius of the

rosette, causes the copy to be much diminished.

 

150. Copying dies. A lathe has been long known in France, and

recently been used at the English mint for copying dies. A blunt

point is carried by a very slow spiral movement successively over

every part of the die to be copied, and is pressed by a weight

into all the cavities; while a cutting point connected with it by

the machine traverses the face of a piece of soft steel, in which

it cuts the device of the original die on the same or on a

diminished scale. The degree of excellence of the copy increases

in proportion as it is smaller than the original. The die of a

crown-piece will furnish by copy a very tolerable die for a

sixpence. But the chief use to be expected from this lathe is to

prepare all the coarser parts, and leave only the finer and more

expressive lines for the skill and genius of the artist.

 

151. Shoe-last making engine. An instrument not very unlike

in principle was proposed for the purpose of making shoe lasts. A

pattern last of a shoe for the right foot was placed in one part

of the apparatus, and when the machine was moved, two pieces of

wood, placed in another part which had been previously adjusted

by screws, were cut into lasts greater or less than the original,

as was desired; and although the pattern was for the right foot,

one of the lasts was for the left, an effect which was produced

by merely interposing a wheel which reversed the motion between

the two pieces of wood to be cut into lasts.

 

152. Engine for copying busts. Many years since, the late Mr

Watt amused himself with constructing an engine to produce copies

of busts or statues, either of the same size as the original, or

in a diminished proportion. The substances on which he operated

were various, and some of the results were shewn to his friends,

but the mechanism by which they were made has never been

described. More recently, Mr Hawkins, who, nearly at the same

time, had also contrived a similar machine, has placed it in the

hands of an artist, who has made copies in ivory from a variety

of busts. The art of multiplying in different sizes the figures

of the sculptor, aided by that of rendering their acquisition

cheap through the art of casting, promises to give additional

value to his productions, and to diffuse more widely the pleasure

arising from their possession.

 

153. Screw cutting. When this operation is performed in the

lathe by means of a screw upon the mandril, it is essentially an

art of copying, but it is only the number