segunda-feira, 12 de maio de 2008


The candle stick above is a piece I made for a client in Glasgow.
The pole and bow lathe have certainly had a long history and have not been solely used for wood turning but also for ceramic and metal work.
Today I have been on the lathe turning bone collars for an old velum portable telescope, the bone is irregular and needed to be softened first, hot water, then placed on a former, a tapered bottle, allowed to cool to hold the more rounded shape and the held on the lathe with some adjustable chucks whilst I firstly cut the inside diameter correct for the tubes and then formed the outside shape to form a collar with a small ring, so as to be able to catch each tube seperately with the fingers and extend the telescope, similar to those used at sea. Then the art is to sand it to a more irregular shape and tint the bone to appear old, in keeping with the velum tubes. One other job today is the repair of the base for an old Rose lathe that once worked its pay in the centre of Birmingham's jewellery quarter


Origins of the Lathe
Since we are dealing here with a specialized form of lathe turning,
it would be well to give some of the history of the lathe itself. The
name, which is a linguistic curiosity, comes from the English lath
which was a pole or split strip of wood, and was used as a spring
power source for early lathes. In India, for example, a lathe was
called a chakra, a wheel, and it is common to other languages than
English that the term for lathe has a relationship to a wheel, or
circle. The lathe is a tool of rotation and the works generated
thereon are always 'solids of rotation'. That is to say that if a
cross-section be taken perpendicular to the axis of rotation, this
section will always be a true circle.

Turning is the process of shaping an object mounted in a lathe into a
rounded form by applying tools against the workpiece as it spins.
Plain turning creates objects whose every section is a perfect
circle. Ornamental turning, however, works upon the plain-turned
shape to apply some form of ornament by means of an externally
powered cutting device. The cut surface which results can evidence
great complexity of decoration. A variety of types of motion and
interaction of workpiece with cutter is possible. The workpiece may
be held stationary by an indexing device while an external cutting
tool is brought in to make a cut; when indexed and the cuts repeated,
this can create a basketwork effect of pattern among many others.
Additionally, the work and cutter may move in a synchronized motion
maintained by means of gear trains much as in the cutting of screw
threads on a machinist's lathe. A rocking motion is also a possible
complication of technique when using a specialized ornamental lathe
called a rose engine. The embellishment of plain-turned objects with
designs can elevate merely utilitarian objects into the realm of the
decorative arts.

The lathe, termed "the engine of civilization," unique amongst
machine tools in that it is the only machine capable of replicating
itself, is also capable of manufacturing all other machine tools. Its
history dates back at least 3000 years. There are extant fragments of
an Etruscan bowl dating to 700 BC. An illustration of a lathe carved
on an Egyptian tomb wall dates to 300 BC. The Egyptians undoubtedly
turned the legs of chairs and stools and other long objects. Though
they did not leave us with descriptions of their lathes, the
Egyptians did describe and picture their potters' wheels and bow
drills, both forms of vertical lathes.
The lathe was certainly known in Grecian and Roman times, though no
accounts remain of it or the tools employed in turning. Cicero and
Pliny refer to the turners or vascularii, and the master Greek
sculptor Phidias is assumed to have turned cups before encrusting
them with ivory and then carving them with chisel and file. Herodotus
is quoting as saying, "But I smile when I see many persons describing
the circumference of the earth, who have no sound reason to guide
them; they describe the ocean flowing round the earth, which is made
circular as if by a lathe." Virgil, as translated by Dryden,
describes in the following passage a process whereby wooden bowls
were plain-turned and ornament was then hand carved upon them:

Two bowls I have well turned of beechen wood;
Both by divine Alcimedon were made;
To neither of them yet the lip is laid.
The lids are ivy: grapes in clusters lurk
Beneath the carving of this curious work.

A primitive apparatus used in India is likely illustrative of many of
these early lathes. The Indian lathe was portable, and set up by the
turner at the site where work was needed. Two wooden poles were
driven in the ground and the work mounted between them on centers
which were simply round nails or spikes driven through the mounting
poles. A bar or rod was then lashed with cords to the two poles to
serve as a toolrest. In use, the turner sat on the ground and guided
the cutting tool edge with his toes while holding the handle with his
hands. Motion was imparted to the workpiece by means of a cord
wrapped around the workpiece which was pulled by a helper. Cutting
could only be done on one-half of the motion, that of the workpiece
towards the tool. Early Persian and Arabian lathes work on a similar
principle, but are more sophisticated in that they are built into a
box and the power is supplied by a bow and string


The Lathe Through The Middle Ages in European History
The lathe was introduced into England at least by 200BC by the Iron
Age Celts. In the West, improvements to the lathe appear to have
arisen from a different method of rotating the lathe conditioned by
the European habit of selecting the erect posture for most mechanical
operations. One end of the driving cord was fastened to a treadle or
stirrup, it was then passed around the workpiece and then the other
end was fastened overhead to a pole or spring above the lathe. Such a
technique greatly increased the power of rotation and left both hands
free for controlling the tool. The paucity of written records leaves
us little information about the lathe during medieval times, and it
is not until the Renaissance that evidence of the use of lathes
appears. Gio Paulo Lomazzo described the oval turning of Leonardo da
Vinci (1452-1519) in 1590. The following verses accompany an
illustration of a turner in the book "Panoplia Omnium," by Hartman
Schopper, published at Frankfort-on-the-Main in 1568:

A turner I:--with unremitting skill,
I turn from yellow box, whate'er you will:
Boxes of shapes unnumbered we produce
And who can tell our boxes' varied use;
There may'st thou store, secure from stranger's view,
Thy noble treasures of the brightest hue,
There too the ball is made, which--wondrous sight!
Struck by the wand, rebounds in varied flight,
Here too the top, that warms the schoolboy's force,
And whirls on level ground its well urged course.

The first book dealing specifically with ornamental turning as well
as 'plain' turning was published by L'Abbe Charles Plumier in 1701.
Joseph Moxon described turnery in his book Mechanick Exercises or the
Doctrine of Handy-Works in 1703. Denis Diderot D'Alembert prepared
the first encyclopedia from 1751 to 1772, and therein illustrates
lathes and the work done on them. The great classic of early turning,
however, is Le Manuel du Tourneur published by L. E. Bergeron in
1796. This comprehensive set of two volumes, containing 96 plates,
was published for the aristocracy rather than for the artisan. In
great detail it illustrates the state of the art at that time. By
this era, lathes had developed into very sophisticated machines from
their humble origins.


The Invention of the Modern Lathe(ca. 1700)
The modern lathe was not actually invented, but was a product of the
refinement of input from many sources. Its evolution was one of
gradual improvement. One key element to this development was the
introduction of a large flywheel separate from the spindle that could
serve to maintain a uniform speed and always allow the lathe to
rotate in the same direction so that cutting could be continuous.
Moxon, in 1677, describes the advantages of this improvement to
powering the lathe:

Besides the commanding heavy Work about, the Wheel rids Work faster
off than the Pole can do; because the springing up of the Pole makes
intermission in running about of the Work; but with the Wheel the Work
runs always the same way; so that the Tool need never be off it,
unless it be to examine the Work as it is doing.

So with a flywheel to store energy and redistribute it with a uniform
motion, and a treadle and crank to allow the turner to stand and pump
power to the machine with his legs, the turner had both hands free to
manipulate tools.

Another important refinement to the lathe was the introduction of
iron bearers for the bed instead of wood. The iron would maintain its
alignment and if a carriage be mounted on a bearer of triangular
section, it would serve to keep it in a true relation to the lathe
axis for its whole length. The accurate bed then served as a platform
for the final refinement which was the moveable carriage connected to
the spindle by means of a gear train. In the 1780's, the French
inventor Jacques de Vaucanson (1709-82) built an industrial lathe
with a sliding tool carriage, advanced by a long screw. Then almost
simultaneously in 1797, Henry Maudslay (1771-1831) in England and
David Wilkinson (1771-1852) in the U.S. improved this lathe by adding
a sliding tool carriage geared to the spindle. By this means, the
carriage mounted with a cutting tool was able to move in
synchronicity with the spindle at a constant speed and the cutting of
accurate and repetitive screw threads became possible. This
breakthrough heralded the age of mass production and interchangeable
parts. With lathes this sophisticated by the end of the 18th century,
ornamental turning began to reach a state of high development.



The Refinement of the Ornamental Lathe
by Holtzapffel, et al.
Generally considered in the same breath with the term "ornamental
turning" is the family name of Holtzapffel. John Jacob Holtzapffel
moved from Alsace to England in about 1785 and opened his engineer's
tool business in London in 1793. His first lathe was sold to a Mr.
Crisp on June 31st 1795, the outfit costing £ 25-4s-10d. When one
considers that today this would be over £ 2000, or $3000US, and that
the skilled mechanic of the day earned less than 8d per hour, this
lathe represented over 3 months wages. All of Holtzapffel's lathes
were numbered, and not all had full ornamental turning apparatus
included. By about 1805, after the Holtzapffel firm had reached
nearly No. 500 in their numbering scheme, almost all lathes had iron
beds instead of the previously used mahogany wood beds. The last
lathe sold was Holtz. No 2557, made in 1913/14 and sold in Nov. 1928.
No other maker of ornamental lathes matched the productivity of the
Holtzapffel family in the field of ornamental lathes.

When John Jacob I died in 1835, about 1600 lathes had been sold by
his firm. Not all were fully equipped as ornamental lathes, but with
the large number that were, quite an impetus was given to ornamental
turning as a leisure occupation in England. The introduction of the
cutting frame by Holtzapffel allowed for significantly more complex
patterns to be cut as compared to what could be done previously with
only the drilling frame. The elder Holtzapffel standardized his screw
threads before 1800, his spindle thread being 9.45 threads per inch
for example, and the firm maintained this standard throughout all the
lathes they manufactured. This standardization was initiated long
before any kind of screw standards were established for industry at

The son of John Jacob I, Charles, who joined the firm in 1827, began
the monumental series of five books that were called Turning and
Mechanical Manipulation in 1835. This ambitious effort, comprising
over 3000 pages and 1600-odd illustrations, was intended to be a
complete survey and overview of all the mechanical arts of the day.
It was not until 1884 that Vol. V was published by the son of Charles
Holtzapffel, John Jacob II. However, it was not until 1894, with the
addition of a revised and enlarged version of Vol. III, that the set
was complete. Today, Vol's. IV and V of this series are known as
the "Bible of Ornamental Turning" because of their wealth of
information about all aspects of the craft of ornamental turning.
Charles managed the firm until his death in 1847. He was considered a
distinguished engineer, developing and inventing various devices. An
obituary notice remarked of him that,

Mr. Holtzapffel probably never put his hand to a machine which he did
not improve, and his practice in the construction of machines has
been more miscellaneous probably than that of any other mechanist,
his workmanship more accurate, and his general mechanical
arrangements more refined...He had all the humility of genius without
its eccentricities, and his heart habitually overflowed with kindness
towarrd everyone around him.

Charles' wife, Amelia, ran the firm until 1853, and in 1867, Charles'
son, John Jacob II, became head of the firm until 1896. He died in
1897. A nephew of Charles, George William Budd, became head of the
firm in 1896. Few ornamental lathes were made after the turn of the
century and the 19th century was known as the zenith of the
ornamental turning lathe. Many lathes were sold to the aristocracy of
England. The earl of Harborough, for instance, bought nine
Holtzapffel lathes between 1812 and 1848. This was certainly not
common, but is instructive of the popularity of these machines once
one developed an affinity for OT.

The contribution of John Jacob Holtzapffel's work was significant in
several respects. As expressed by Walshaw (see Bibliography), "First,
he brought the cost of the machine down to a figure which a
mere 'gentleman' (or even a prosperous tradesman) could afford, and,
second, the design was both elegant and functional." His designs were
much improved over the lathes previously made on the continent of
Europe. Holtzapffel also was a master of marketing apparatus to his
clients over time. Improvements and additions to apparatus increased
the capability of his equipment and induced his clients to continue
to be his customers. The remarkable set of books by the family were,
in effect, an extensive set of owner's manuals for their machines.

In addition to the Holtzapffels, other makers produced ornamental
lathes. Among them were the ornamental lathes of John Evans (1843-
1919) which were of high quality and counted some improvements over
the Holtzapffel lathes to their advantage. A large number of lathes
were attributed to his firm, and improved overhead drives, sliderests
and cutting frames marked the work of this talented machinist. He
also wrote a book on ornamental turning which some find much more
easily understandable than the Holtzapffel books. George Birch and
Company made a few ornamental lathes, but they were essentially
engineers' metalworking tools which were given the necessary
components to do ornamental turning. George Goyen, a retired South
American railway engineer who took to making lathes as a hobby, is
generally credited with singlehandedly creating the finest ornamental
lathes ever produced. He probably made his lathes for his friends'
amateur use and only ten Goyen lathes are known to exist. There were
other makers such as George Plant, George Hines, Hulot, James Munro,
Joseph Fenn and James Lukin and many of them made lathes of a caliber
of workmanship equal to a Holtzapffel. Lukin also wrote a book (see
Bibliography) on ornamental turning and Frank Knox considered
it "second only to Holtzapffel in usefulness," as "Lukin clarifies
much of what Holtzapffel leaves unclear." There were indeed other
toolmakers who made ornamental lathes, but these makers are those who
have left us with extant examples of their machines.

A typical example of an array of ornamental cutters is seen in Evans'
book. This was an assortment of cutters that would be in a basic
collection from any of the ornamental lathe makers. Cutters such as
these were mounted in the universal cutting frame, the horizontal
cutting frame or the vertical cutting frame and could produce a great
variety of pattern, especially if the cuts from several cutters were
combined in the design of the pattern.

Many specialized chucks and apparatus comprised a complete ornamental
turning lathe package.Typical of the presentation of apparatus for a
Holtzapffel OT lathe is this array of gears and accessories for the
spiral and reciprocator apparatus. They are housed in a finely-
crafted mahogany box, and are beautiful to look at and in use. A
drill frame was necessary to do work in which the cutter rotated as a
modern router bit would. Pearls and other features could be created
depending upon the profile of the cutter. An eccentric cutting frame
allowed for shallow circles to be cut with adjustments to vary the
diameter of the circle cut and its displacement from the central axis
of the piece. With careful thought and design, very intricate
patterns of a geometric nature could be rendered by this technique.

Other apparatus included a variety of special-purpose chucks, such as
the eccentric and rectilinear chucks. It was also possible to create
ellipses and, by means of a compensating index, create equal
divisions of the ellipse. A geometric chuck comprised of a complex
set of interacting gears would allow tracings to be made that would
demonstrate complex geometric curves, such as the epicycloidal
pattern. Much ornamental turning was done in ivory, as it produced
the finest cuts and allowed for great delicacy of pattern due to its
hardness and strength. At times, incredibly intricate work was
performed by the Holtzapffel firm to illustrate to the public the
capabilities of their machines.

A beautiful example of the finest work put out by the Holtzapffel is
in this Rose Engine Lathe, one of only 8 ever made. These were a
specialized type of ornamental lathe in which the headstock rocked
back and forth as controlled by a rubber moving against a rosette or
cam-like pattern mounted on the spindle at the same time as the lathe
spindle rotated. Rose engine work often reveals flower patterns, and
convoluted, symmetrical, multi-lobed organic patterns. It has the
potential to be very complex and to produce beautiful and unique
patterns unlike any other on the ornamental lathe.

Excellent engraved plates of ornamental turning and an extensive
depiction of various OT apparatus can be found in Holtzapffel Vol. V
(see Bibliography). Much of the historic ornamental turning machinery
that has survived is now held by collectors or is in museums. Only a
small number of machines are still being used for their intended
purpose. Most of this machinery bespeaks an era of unbounded optimism
and is beautifully made and a joy to view and use. They represent a
time in history when quality still meant "excellence." To my view,
the makers and users of this machinery were obviously on a quest to
participate in the experience of beauty and "a thing done well," and
from our own perspective in time, succeeded admirably.
Here is an extract from the site Regia Anglorum,

Timber was the most important resource for the Anglo-Saxons and Vikings. The early medieval carpenter was not only skilled in working the wood, but also in selecting the correct timber and shape for the job. If the finished item needed to have a curve in it, the carpenter would select a piece of timber that had the correct natural curve. You can use natural junctions where a branch joins to the tree as joints that have grown to suit a job that you had in mind. These natural joints are stronger than man-made ones and save the carpenter a lot of time creating joints. Wherever possible they would 'follow the grain' to leave the finished product as strong as possible.

To a certain extent, all the peoples who lived then managed their woodlands, although if a tree needed to come down for a building let's say, as far as we know they didn't replant to replace that tree deliberately. A thousand years ago, trees were still a resource that would have seemed limitless. It takes for example over 80-90 years for an Oak tree to become large enough to be useful. Large scale timber production had yet to make the impact it would later. A large stand of trees felled would just be providing clearance for yet more farmland. The Vikings are regarded to some extent today in Iceland as 'environmental terrorists', as they eventually felled all of the trees that had once grown there. The Iceland we see today has been irrevocably changed due to their habits.

A great deal of Saxon and Viking woodwork was done 'green,' that is the timber was not seasoned (dried out over time) before working. This meant that the timber could be split easily (green oak can be split with a seasoned wooden wedge), and need not be sawn. The big advantage of using cleft (meaning split) timber is that it is less likely to crack as it dries.

Most of the 'roughing out' and shaping was done with axes and adzes. The saw has obvious advantages. It can cut out a straight piece of timber every time, splitting can result in planks that are twisted etc. But the trouble with saws was that they were very expensive and difficult to maintain and make. At the time of the Domesday Book in 1086, only 13 saws were recorded in the kingdom. These were probably large saws for what is called 'ripping' down the beam of timber to create planks, as much smaller bow saws are routinely shown in manuscripts.

The trimming and shaping with Adzes and Axes is quite a wasteful process as well. With saws, large pieces of wood can be separated from the job at hand, leaving you with a reasonable piece of wood that can be utilised for other smaller jobs. The Adzes and Axes just convert the unwanted timber into pieces only suitable for the fire. However, the bark would be stripped off for the tanners, as it contains tannin, especially if the tree had been an oak, alder or elm, and the bast fibres that lie just under the bark would also be pulled off to make rope and other ties. Willow, lime and again oak trees give some of the most useful bast fibres. And ultimately, any left over timber could be used in the Charcoal making process, or just burnt to keep the workers in the woods warm in the Autumn.

Um comentário:

Graça Barroso disse...

fofo, acho que vou precisar dessas informações no curso de Ouro Preto, estão ótimas!fofa