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On Contriving Machinery
318. The power of inventing mechanical contrivances, and of ...

Of Printing From Cavities
83. The art of printing, in all its numerous departments, is ...

Of Copying By Moulding
112. This method of producing multitudes of individuals havi...

Saving Time In Natural Operations
47. The process of tanning will furnish us with a striking i...

On The Position Of Large Factories
277. It is found in every country, that the situation of lar...

On The Effect Of Machinery In Reducing The Demand For Labour
404. One of the objections most frequently urged against mac...

Registering Operations
65. One great advantage which we may derive from machinery is...

Increase And Diminution Of Velocity
32. The fatigue produced on the muscles of the human frame d...

On The Method Of Observing Manufacturies
160. Having now reviewed the mechanical principles which reg...

Printing From Surface
91. This second department of printing is of more frequent a...

On The Exportation Of Machinery
437. A few years only have elapsed, since our workmen were n...

Of The Identity Of The Work When It Is Of The Same Kind And Its Accuracy When Of Different Kinds
79. Nothing is more remarkable, and yet less unexpected, than...

On Combinations Amongst Masters Or Workmen Against Each Other
353. There exist amongst the workmen of almost all classes, ...

Of Money As A Medium Of Exchange
166. In the earlier stages of societies the interchange of t...

On The Causes And Consequences Of Large Factories
263. On examining the analysis which has been given in chapt...

Extending The Time Of Action Of Forces
45. This is one of the most common and most useful of the em...

Economy Of The Materials Employed
77. The precision with which all operations by machinery are ...

Of Copying
82. The two last-mentioned sources of excellence in the work ...

Distinction Between Making And Manufacturing
163. The economical principles which regulate the application...

On The Influence Of Durability On Price
197. Having now considered the circumstances that modify what...

Of The Identity Of The Work When It Is Of The Same Kind And Its Accuracy When Of Different Kinds

79. Nothing is more remarkable, and yet less unexpected, than
the perfect identity of things manufactured by the same tool. If
the top of a circular box is to be made to fit over the lower
part, it may be done in the lathe by gradually advancing the tool
of the sliding-rest; the proper degree of tightness between the
box and its lid being found by trial. After this adjustment, if a
thousand boxes are made, no additional care is required; the tool
is always carried up to the stop, and each box will be equally
adapted to every lid. The same identity pervades all the arts of
printing; the impressions from the same block, or the same
copperplate, have a similarity which no labour could produce by
hand. The minutest traces are transferred to all the impressions,
and no omission can arise from the inattention or unskilfulness
of the operator. The steel punch, with which the cardwadding for
a fowling-piece is cut, if it once perform its office with
accuracy, constantly reproduces the same exact circle.

80. The accuracy with which machinery executes its work is,
perhaps, one of its most important advantages: it may, however,
be contended, that a considerable portion of this advantage may
be resolved into saving of time; for it generally happens, that
any improvement in tools increases the quantity of work done in a
given time. Without tools, that is, by the mere efforts of the
human hand, there are, undoubtedly, multitudes of things which it
would be impossible to make. Add to the human hand the rudest
cutting instrument, and its powers are enlarged: the fabrication
of many things then becomes easy, and that of others possible
with great labour. Add the saw to the knife or the hatchet, and
other works become possible, and a new course of difficult
operations is brought into view, whilst many of the former are
rendered easy. This observation is applicable even to the most
perfect tools or machines. It would be possible for a very
skilful workman, with files and polishing substances, to form a
cylinder out of a piece of steel; but the time which this would
require would be so considerable, and the number of failures
would probably be so great, that for all practical purposes such
a mode of producing a steel cylinder might be said to be
impossible. The same process by the aid of the lathe and the
sliding-rest is the everyday employment of hundreds of workmen.

81. Of all the operations of mechanical art, that of turning
is the most perfect. If two surfaces are worked against each
other, whatever may have been their figure at the commencement,
there exists a tendency in them both to become portions of
spheres. Either of them may become convex, and the other concave,
with various degrees of curvature. A plane surface is the line of
separation between convexity and concavity, and is most difficult
to hit; it is more easy to make a good circle than to produce a
straight line. A similar difficulty takes place in figuring
specula for telescopes; the parabola is the surface which
separates the hyperbolic from the elliptic figure, and is the
most difficult to form. If a spindle, not cylindrical at its end,
be pressed into a hole not circular, and kept constantly turning,
there is a tendency in these two bodies so situated to become
conical, or to have circular sections. If a triangular-pointed
piece of iron be worked round in a circular hole the edges will
gradually wear, and it will become conical. These facts, if
they do not explain, at least illustrate the principles on
which the excellence of work formed in the lathe depends.

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