Wood Turning
From the
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Woodturning is a form of woodworking that is used
to create wooden objects on a lathe. Woodturning differs from most
other forms of woodworking in that the wood is moving while a
(relatively) stationary tool is used to cut and shape it. Many
intricate shapes and designs can be made by turning wood.
There are two distinct methods of turning wood: spindle turning and
faceplate turning. In spindle turning, the grain of the wood runs
lengthwise, parallel to the bed of the lathe. In face plate
turning, the grain of the wood runs perpendicular to the axis of
rotation. Most bowls, platters and many vessels are face plate
turned. Pens, furniture legs, spindles, and some vessels are
spindle turned. It is the orientation of the grain that determines
the method in use. Spindle turning is named for the type of product
originally produced, while faceplate turning is named for an early
method of attaching the material to the lathe.
The distinction between spindle turning and faceplate turning is
due to the fibrous nature of the material. When wood is cut in such
a way that the fiber being cut is not supported by the fiber below
it, it tends to separate and tear. This "tearout" exhibits a rough,
highly undesirable surface texture and greatly reduces the value of
any product exhibiting it. The direction of cut is different in
spindle turning and faceplate turning because cutting in the wrong
direction can cause tearout. Spindle turning cuts are made from
high points toward the axis on the outside of the piece, and from
the axis toward the outside when hollowing. When faceplate turning,
the opposite applies.
History
The origin of woodworking dates to around 1300BC when the Egyptians
first developed a two-person lathe. One person would turn the wood
with a rope while the other used a sharp tool to cut shapes in the
wood. The Romans improved the Egyptian design with the addition of
a turning bow. Early bow lathes were also developed and used in
Germany, France and Britain. In the Middle Ages a pedal replaced
hand-operated turning, freeing both the craftsman's hands to hold
the woodturning tools. The pedal was usually connected to a pole,
often a straight-grained sapling. The system today is called the
"spring pole" lathe. Spring pole lathes were in common use into the
early 20th Century. A two-person lathe, called a "great lathe",
allowed a piece to turn continuously (like today's power lathes). A
master would cut the wood while an apprentice turned the crank.
The term "bodger" stems from pole lathe turners who used to make
the chair legs and spindles. A bodger would typically purchase all
the trees on a plot of land, set up camp on the plot, and then fell
the trees and turn the wood. The spindles and legs that were
produced were sold in bulk, for pence per dozen. The bodger's job
was considered unfinished because he only made component parts. The
term now describes a person who leaves a job unfinished, or does it
badly.
During the industrial revolution the lathe was motorized, allowing
turned items to be created in less time. The motor also produced a
greater rotational speed for the wood, making it easier to quickly
produce high quality work. Today most commercial woodturning is
done by computer-operated machinery allowing for mass-production
that can be created with accurate precision and without the cost of
employing craftsmen. Despite this, there is still a demand for
hand-turned products. Woodturning is also a hobby enjoyed by many
people.
Modern professional woodturners are typically either "production"
turners producing large quantities of functional pieces, or
artistic turners producing smaller numbers of pieces, often
enhanced after turning by carving, piercing, coloring, applying
pyrography, gilding, or a number of other techniques to produce
objects for the art market.
Woodturning Tools
Turning tools are generally made from three different types of
steel, carbon steel, high speed steel (HSS), and more recently
powdered metal. Comparing the three types, high speed steel tools
maintain their edge longer, requiring less frequent sharpening than
carbon steel, but not as long as powdered metal tools. The harder
the type of high speed steel used, the longer the edge will
maintain sharpness. Powdered steel is even harder than HSS, but
does not take an edge that is as sharp as HSS. Unlike other edged
woodworking tools, woodturning tools require more frequent
sharpening, because the wood passes at a great speed. To maintain a
clean cut, the sharpness of the tools edge must be maintained. The
sharpening process requires either skill of the craftsman, or one
of the many available sharpening jigs, which facilitate maintaining
a specific bevel on the tool.
Types
" roughing gouge - a wide fluted gouge used to initially round a
wooden spindle, and to roughly shape it. Generally not intended for
cutting end grain due to the large cut it takes and the relatively
weak tang connecting the blade to the handle. Unsafe for making
bowls or any faceplate work.
" spindle gouge or detail gouge - a shallow fluted gouge used to
create details on spindles, including beads (raised portions of the
turning typically semi-circular in cross section) and coves
(relieved portions of the turning).
" bowl gouge - a deep fluted gouge used to turn the outside and
inside of bowls and vessels. Often has a thicker shaft and longer
handle than a spindle gouge because it has to cut farther away from
the handrest.
" skew chisel - a wide, steeply pointed chisel with the edge
running at an angle to the length of the tool. Used to smooth flat
spindles, cut beads, and add details. Skew chisels are only used on
spindle work (never on faceplate work) and are honed after
sharpening to create a razor edge.
" parting tool - a pointed tool used to separate (part off) work
from the lathe, and to create a straight edge separating large and
small diameter sections - wide parting tools also called bedans are
used to create evenly sized spindle sections.
" hollowing tool - many different types of tools used to cut out
the deep sections of steep bowls, vases and hollow vessels. Often
with very long handles, to maintain enough leverage when working in
a deep vessel, far away from the handrest.
" scraper - a tool that scrapes the wood fibers instead of cutting
- these are used to smooth off wooden items cut with other tools,
and to shape items that are not possible or difficult to shape with
gouges. A sharp scraper has a burr at the edge which cuts the wood,
only a dull scraper actually scrapes.
" bowl saver - a tool used to core out the inside part of a bowl,
allowing the waste piece to be used to create a smaller bowl, and
to limit the amount of wood chips created when hollowing out a
bowl.
" auger - a drill bit used to drill a hole partway or all the way
through a wooden item. For cutting the hole for a lamp cord, or as
the first step when hollowing out a bowl or vessel
" chatter tool - a flexible scraper used to add decorative chatter
marks to turned items
" wire - a simple wire, sometimes with handles attached at either
side, for the purpose of burning lines into the piece with
friction.
" there are also several tool types for special purposes, as well
as tools that are a combination design of the above tools, i.e.
skew/chisel combinations, thread cutting tools, ring cutting tools,
medium fluted gouges, etc.
Other Techniques
" eccentric turning - turning a single piece multiple times, upon
different axes each time.
" oval or elliptical turning - turning a piece using an accessory
mounted to the headstock that changes the center of rotation of the
piece in time with the rotation, so that a cutting tool held in a
fixed position on the tool-rest cuts an oval rather than a round
path on the workpiece
" therming - mounting a carrier between centers, and then mounting
the small workpiece(s) to the carrier, so that the axis of the
headstock/tail-stock does not pass through any of the workpieces,
and each workpiece gets cut only on one face. As noted in
Wood-turning Methods by Mike Darlow, the etymology of the term
"therming" comes via a corruption of the name of the Greek god
Hermes, who was often represented as a statue set atop a plinth
with a construction characteristic of thermed work.
" segmented turning - a method of woodturning where the wood blank
is constructed from many individual pieces of wood (segments) which
are laminated together before being turned. Many interesting
patterns can be generated through the process of lamination and
shaping on the lathe.
" green or wet turning - turning wood while its moisture content is
above equilibrium. Often done when the wood is newly felled. May be
turned to finished thickness, in which case the differential
shrinkage of the wood will result in a finished piece that is not
perfectly round. Alternatively, it may be "rough turned". Rough
turning involves turning the piece only to its general shape,
leaving enough thickness so that after turning it can be allowed to
dry to equilibrium moisture content and distort. The advantage over
first drying the wood then turning is that a rough turned piece
dries faster, will probably distort instead of split as massive
wood is want to do, and that wet wood turns better, since it
creates less dust. Rough turning is an inexact science: turning
wood too thick will lead to splits, turning wood too thin will lead
to distortion that cannot be removed, because not enough thickness
is left. Once dry, it is mounted on the lathe a second time and
turned to its final form. Rough turning is typically used on most
functional work and some artistic pieces.
" natural edge work - pieces which include the outside of the tree
trunk or limb as the edge of the piece. Typically artistic
turnings, usually bowls or hollow vessels, and usually green turned
to final dimension. May include the bark or not, but pieces with
bark should not have any bark damaged or missing.
" ornamental turning - also known as OT, a method in which the
piece is mounted upon a rocking headstock, and a spinning tool is
used to cut out exotic and decorative patterns Safety When
woodturning, it is important to wear certain personal protective
equipment (PPE). Loose clothing should not be worn, all jewelry
should be removed, and long hair should be tied back. Wood shavings
generated during turning will also need to be periodically
removed.
" Eye protection is a necessity when woodturning. There are several
PPE available for eye protection such as safety goggles, glasses
and visors, some of which feature built-in respirators. Although
all of these are adequate, for the highest level of protection, a
visor that protects the entire head from dust and debris should be
worn.
" Respiratory equipment and dust collection systems are also
important when woodturning or doing any type of woodworking that
creates dust. This can range from a simple disposable dust mask, to
a full face helmet with built in respirator. Most stand alone
respiratory equipment will interfere with dust shields and visors,
so devices that incorporate both are available. Many woods create
dust that is actually a health hazard. For example, cocobolo
(granadillo) dust is known to be toxic (toxic shock). Many people
are sensitive to oils carried in walnut, locust, and oak
sawdust.
" Ear protection Compared to other power tools, a lathe is a
relatively quiet machine. Ear protection should be used if noise is
excessive, this may be due to motor (fan) noise from a shop dust
collector, or the combination of wood and tool being used.
" Hand/Skin protection Gloves should not be used with rotating
equipment, since there's always a risk of getting tangled in the
machine. Nevertheless, some woods provide splinters that not only
puncture skin, but also cause festering sores and/or skin
irritation. This subject continues to be debated in the
community.
" Foot protection. Protective footwear, often leather steel toe
boots, are required for any type of shop activity.
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