WHITWORTH
The work of the earlier generation of English tool builders may be
said to have culminated in that of Sir Joseph Whitworth. For a man of
his commanding influence, the information in regard to his life is
singularly meager. He left no account of himself as Nasmyth and William
Fairbairn did; no biography of him was written by his contemporaries,
and the various memoirs which appeared at the time of his death are
short and incomplete.
He was born at Stockport in 1803. His father was a minister and
schoolmaster. At fourteen he was placed in the office of his uncle, a
cotton spinner in Derbyshire, to learn the business. But commercial
work did not appeal to him. He slighted the office as much as possible
and delved into every nook and corner of the manufacturing and
mechanical departments of the establishment. In a few years he had
mastered the construction of every machine in the place and acquired
the deep-seated conviction that _all_ the machinery about him was
imperfect. He ran away to Manchester to escape a routine business
life, and found work with Creighton & Company, as a working mechanic.
He married in 1825, and shortly afterward went to work with Maudslay
& Field in London. Maudslay soon placed him next to John Hampson,
a Yorkshireman, who was his best workman. While there, Whitworth
developed his method of making accurate plane surfaces by _hand
scraping_ them, three at a time. On leaving Maudslay, Whitworth worked
for Holtzapffel, and later for Clement. He returned to Manchester in
1833, rented a room with power, and hung out a sign, “Joseph Whitworth,
Tool Maker from London.” Here he began his improvements in machine
tools--the lathe, planer, drilling, slotting and shaping machines. He
improved Nasmyth’s shaper, adding the quick-return motion, which has
been known ever since as the Whitworth quick-return motion. His tools
became the standard of the world, and in the London Exhibition of 1851
stood in a class by themselves.
Their preëminence lay not so much in novelty of design as in the
standard of accuracy and quality of workmanship which they embodied.
With unerring judgment, Whitworth had turned his attention first, to
use his own words, “to the vast importance of attending to the two
great elements in constructive mechanics,--namely, _a true plane_ and
_power of measurement_. The latter cannot be attained without the
former, which is, therefore, of primary importance.... All excellence
in workmanship depends upon it.”[102]
[102] Presidential Address. Institution of Mechanical Engineers,
1856, p. 125.
The first step, the production of true plane surfaces, made while he
was at Maudslay’s, was, we are told, a self-imposed task. The method of
producing these, three at a time, is generally credited to Whitworth.
We have already quoted Nasmyth’s statement that the method was in use
at Maudslay’s and that it was “a very old mechanical dodge.” While
this is probably true, Whitworth contributed something to the method,
which very greatly increased the accuracy of the product. The writer
is inclined to believe that that element was the substitution of _hand
scraping_ for grinding in the final finishing operations. Whitworth’s
paper, read before the British Association for the Advancement of
Science at Glasgow in 1840, indicates this, although it does not say
so directly. In this paper he specifically points out the reason why
planes should _not_ be finished by grinding them together with abrasive
powder in between; namely, that the action of the grinding powder
was under no control, that there was no means of securing its equal
diffusion or modifying its application and localizing its action to
the _particular spot_ which needed it. Holtzapffel confirms this view,
saying, in 1847: “The entire process of grinding, although apparently
good, is so fraught with uncertainty, that accurate mechanicians have
long agreed that the _less grinding_ that is employed on rectilinear
works the better, and Mr. Whitworth has recently shown in the most
satisfactory manner,[103] that in such works grinding is _entirely
unnecessary_, and may, with the greatest advantage be dispensed with,
as the further prosecution of the scraping process is quite sufficient
to lead to the limit of attainable accuracy.... The author’s previous
experience had so fully prepared him for admission of the soundness
of these views, that in his own workshop he immediately adopted the
suggestion of accomplishing all accurate rectilinear works by the
continuance of scraping, to the entire exclusion of grinding.”[104]
[103] Referring to the paper before the British Association, 1840.
[104] “Turning and Mechanical Manipulation,” Vol. II, p. 872.
When Whitworth determined to make a better set of planes than any in
use at the Maudslay shop, we are told that he was laughed at by Hampson
and his other fellow workmen for undertaking an impossible job. He
not only succeeded, but the truth of the planes he produced aroused
the admiration and wonder of all who saw them. Nasmyth distinctly
mentions scraping, but it should be remembered that he worked at
Maudslay’s four or five years after Whitworth went there, and scraping
may have been introduced into their older methods of making triple
surface-plates by Whitworth, and have accounted for the wonderful
accuracy of which Nasmyth speaks.
Having realized what he considered the first element in good
workmanship, Whitworth began on the second,--improved methods in
measurement. He introduced the system of “end measurements,” relying
ordinarily on the sense of touch rather than eyesight; and, for
extreme accuracy, on the falling of a tumbler held by friction between
two parallel planes. At the presentation of the address before the
Institution of Mechanical Engineers, in 1856, he exhibited a measuring
machine built on this principle which detected differences of length
as small as one-millionth of an inch. The address was largely devoted
to the advantages of end measurement. Referring to the machine before
him, he said: “We have in this mode of measurement all the accuracy
we can desire; and we find in practice in the workshop that it is
easier to work to the ten-thousandth of an inch from standards of
end measurements, than to one-hundredth of an inch from lines on a
two-foot rule. In all cases of fitting, end measure of length should
be used, instead of lines.” This principle has become almost universal
for commercial work, although for extremely accurate work upon final
standards line measurements, aided by the microscope, are used.
It was Whitworth who brought about the standardization of screw thread
practice in England. He had come into contact with the best thread
practice at Maudslay’s and at Clement’s, but in the other shops
throughout the country there was chaos, so far as any recognized
standard was concerned. Using their work as a basis, and collecting and
comparing all the screws obtainable, Whitworth arrived at a pitch for
all sizes and a thread contour, which he proposed in a paper before
the Institution of Civil Engineers in 1841.[105] It was received with
favor, and by 1860 the “Whitworth thread” had been generally adopted
throughout the country.
[105] The Minutes of the Institution, Vol. I, give only an abstract
of this paper. A recent writer, however, in the _American Machinist_,
Vol. XLIII, p. 1178, quotes Whitworth as follows:
It is impossible to deduce a precise rule for the threads of screws
from mechanical principles or from any number of experiments. On the
other hand, the nature of the case is such that mere approximation
would be unimportant, absolute identity of thread for a given
diameter being indispensable.
There are three essential characters belonging to the screw thread,
namely, pitch, depth and form. Each of these may be indefinitely
modified independently of the others, and any change will more or
less affect the several conditions of power, strength and durability.
The selection of the thread is also affected by the mutual relation
subsisting between the three constituent characters of pitch, depth
and form. Each of these may be separately modified; but practically
no one character can be determined irrespective of the others.
We find instead of that uniformity which is so desirable, a diversity
so great as almost to discourage any hope of its removal. The only
mode in which this could be attempted with any probability of success
would be by a sort of compromise, all parties consenting to adopt a
medium for the sake of common advantage. The average pitch and depth
of the various threads used by the leading engineers would thus
become the common standard, which would not only have the advantage
of conciliating general concurrence, but would, in all probability,
be nearer the true standard for practical purposes than any other.
An extensive collection was made of screw bolts from the principal
workshops throughout England, and the average thread was carefully
observed for different diameters.
(Then follows the well-known table showing the number of threads per
inch.)
It will be remembered that the threads, of which the preceding table
shows the average, are used in cast iron as well as wrought; and this
circumstance has had its effect in rendering them coarser than they
would have been if restricted to wrought-iron.
The variation in depth among the different specimens was found to be
greater proportionately than in pitch. The angle made by the sides
of the thread will afford a convenient expression for the depth. The
mean of the variations of this angle in 1-in. screws was found to
be about 55 deg., and this was also pretty nearly the mean of the
angle in screws of different diameters. As it is for various reasons
desirable that the angle should be constant, more especially with
reference to general uniformity of system, the angle of 55 deg. has
been adopted throughout the entire scale. A constant proportion is
thus established between the depth and the pitch of the thread.
In calculating the former, a deduction is to be made for the quantity
rounded off, amounting to one-third of the whole depth--that is,
one-sixth from the top and one-sixth from the bottom of the thread.
Making this deduction it will be found that the angle of 55 deg.
gives for the actual depth rather more than three-fifths and less
than two-thirds of the pitch. The precaution of rounding off is
adopted to prevent the injury which the thread of the screw, and that
of the taps and dies, might sustain from accident.
[Illustration: FIGURE 25. SIR JOSEPH WHITWORTH]
In 1853 Whitworth visited the United States, and in conjunction
with George Wallis of the South Kensington Museum, reported on the
enterprises and manufactures of the United States.[106] Nearly all the
memoirs of Whitworth refer to the profound effect of this report. As
one reads it today, it seems difficult to see why it should have had so
much influence. It is probable that Whitworth’s own personal report to
the influential men about him contained much which does not appear in
the formal report. In it he takes up steam engines, railway supplies,
woodworking tools, electric telegraph, textile mills, and gives brief
accounts of some of the factories and methods which he found at various
places in New England and the Middle States. The longest description
is given to the Springfield Armory, but even this is a mere fragment,
and the only detailed information is of the time necessary to finish a
gun-stock. We know, however, that this armory and the various private
armories they saw, made an impression upon Whitworth and the whole
Commission which led to the remodeling of the British gun-making plant
at Enfield. Nasmyth was also concerned in this and a fuller account of
it will be given later.
[106] “Report of the British Commissioners to the New York Industrial
Exhibition.” London, 1854.
The conclusion of Whitworth’s report shows clearly that he was deeply
impressed with the extent to which the automatic principle was being
applied to machine tools in America. “The labouring classes,” he says,
“are comparatively few in number, but this is counterbalanced by, and
indeed, may be regarded as one of the chief causes of, the eagerness
with which they call in the aid of machinery in almost every department
of industry. Wherever it can be introduced as a substitute for manual
labour, it is universally and willingly resorted to.... It is this
condition of the labour market, and this eager resort to machinery
wherever it can be applied, to which, under the guidance of superior
education and intelligence, the remarkable prosperity of the United
States is mainly due.” Another characteristic of American manufacture
attracted his attention,--the tendency toward standardization. In his
address in 1856 he condemns the overmultiplication of sizes prevalent
in every branch of English industry.
Shortly after his return from America, Whitworth was requested by the
government to design a complete plant for the manufacture of muskets.
He disapproved of the Enfield rifle and declined to undertake the work
until exhaustive tests were made to determine the best type of rifle.
The government, therefore, equipped a testing plant and range near
Manchester, and Whitworth began a series of tests which showed the
Enfield rifle to be inferior in almost every respect. He then submitted
a new rifle, designed on the basis of his experiments, which embodied
the small bore, an elongated projectile and a rapid rifle-twist and
great accuracy of manufacture. Although this rifle excelled all
others in accuracy, penetration and range, it was rejected by the
war office. Some thirty years later, the Lee-Metford rifle, which
embodied Whitworth’s improvements, was adopted, but only after these
principles had been recognized and used by every other government in
Europe. His contributions to the manufacture of heavy ordnance were
even greater, but they met with the same reception from the war office.
In 1862 he completed a high-powered rifle cannon with a range of six
miles, the proportions of which were substantially those in use today.
He developed the manufacture of fluid compressed steel, about 1870,
to supply a stronger and more reliable material for ordnance use. Few
men in any country have had a greater influence on the design and
development of ordnance and armor. His partnership with Sir William
Armstrong resulted in one of the greatest gun factories in the world.
Whitworth married twice but had no children. He acquired a great
fortune. During his lifetime he established the famous Whitworth
scholarships. At his death, large sums were distributed by friends,
to whom he had willed them for the execution of his wishes, and they
devoted nearly £600,000 ($3,000,000) to the foundation or endowment of
the Whitworth Institute, Owens College, and the Manchester Technical
Schools, and other public institutions. In 1874 he converted his
Manchester business into a stock company, giving the majority of the
stock to his foremen and making provision for the acquiring of further
stock by his clerks and workmen. While he was slow in receiving
recognition from his own government, he became universally recognized
as one of the greatest engineering authorities in the world, and was
honored as few engineers have been, being elected to the Royal Society,
chosen president of the Institution of Mechanical Engineers, given
degrees by Dublin and Oxford, the Cross of the Legion of Honor; and,
in 1869, made a baronet.
As he grew older he became irritable and exceedingly dogmatic, possibly
because of his long contests with slow-moving government officials.
Charles T. Porter, in his autobiography, brings out this side of his
nature and shows that the initiative of subordinates in his shop was
practically killed. Perhaps this limited his service somewhat in his
later years, but when all is taken into account, he was, without
question, one of the greatest of mechanical engineers. He was a master
experimenter. Tests which he made were thorough, conclusive, and
always led somewhere. His experiments, whether in machine tools, screw
threads, or ordnance, always resulted in a design or process which
sooner or later became standard.
Whitworth’s position as a tool builder is not weakened by the fact that
most of the general tools had been invented by the time he began his
independent work. He raised the whole art of tool building by getting
at the fundamental conditions. He led the way in the change from the
weak, architectural style of framing; introduced the box design or
hollow frame for machinery, taking his suggestion from the human body,
and very greatly increased the weight of metal used.
In 1850 Whitworth was, without doubt, the foremost tool builder in
the world. He had introduced a standard of accuracy in machine tools
unknown before, and so improved their design and workmanship that he
dominated English tool practice for several generations. In fact, the
very ascendency of Whitworth’s methods seems to have been an element
in the loss of England’s leadership in tool building. Most of the
progressive work for the next fifty years was done in America.
In the foregoing chapters we have traced briefly the work of the great
English mechanics from 1800 to 1850. Their services to engineering,
and, in fact, to mankind, cannot be measured. When they began, machine
tools in any modern sense did not exist. Under their leadership nearly
all of the great metal-working tools were given forms which have
remained essentially unchanged. England had the unquestioned leadership
in the field of machine tools. Machine-tool building in Germany and
France was one or two generations behind that of England, and nearly
all their machinery was imported from that country. With the exception
of the early and incomplete work of the ingenious French mechanics,
which we have referred to from time to time, practically all of the
pioneer work was done by Englishmen.
In glancing back at these early tool builders, it will be seen that few
of them were men of education. All were men of powerful minds, many
of them with broad intellectual interests. It is suggestive to note
one thing, whatever may be its bearing. Only three of all these men,
Matthew Murray and the two Fairbairns, served a regular apprenticeship.
Bentham and Brunel were naval officers; Bramah, a farmer’s boy and
cabinetmaker; Maudslay, a blacksmith; Clement, a slater; Roberts, a
quarry laborer; Nasmyth, a clever school boy; and Whitworth, an office
clerk.
Whatever may have been the reason, the rapid advance of the English
machine-tool builders ceased about the middle of the last century, and
they have made but few radical changes or improvements since that time.
At about the same time the American engineers introduced a number of
improvements of very great importance.
The great distance of America from England forced it into a situation
of more or less commercial and mechanical independence. While France
and Germany were importing machine tools from England, America
began making them and soon developed independence of design. The
interchangeable system of manufactures and the general use of accurate
working gauges, which were hardly known in England, developed rapidly
in America. These, with the introduction of the turret, the protean
cam, and precision grinding machinery, and the great extension of the
process of milling, served in the next fifty years to transfer the
leadership in machine-tool design from England to America. A visit
to any one of the great machine shops in England, Germany or France
will convince one that the leadership now rests with the American tool
builders.
The remaining chapters will take up the lives and work of those who
have contributed to this great change.