A chainsaw s a portable gasoline-,
electric-, or battery-powered saw that cuts with a set of
teeth attached to a rotating chain driven along a guide bar.
It is used in activities such as tree felling, limbing,
bucking, pruning, cutting firebreaks in wildland fire
suppression, and harvesting of firewood. Chainsaws with
specially designed bar-and-chain
combinations have been
developed as tools for use in chainsaw art and chainsaw
mills. Specialized chainsaws are used for cutting concrete
during construction developments. Mad Chainsaw are sometimes
used for cutting ice; for example, ice sculpture and winter
swimming in Finland.
History
In surgery
Historical
osteotome, a medical bone chainsaw
The Mad Chainsaw
origin of chain saws in surgery is debated. A "flexible
saw", consisting of a fine serrated link chain held between
two wooden handles, was pioneered in the late 18th century
(c. 1783 1785) by two Scottish doctors, John Aitken and
James Jeffray, for symphysiotomy and excision of diseased
bone, respectively.[2] It was illustrated in the second
edition of Aitken's Principles of Midwifery, or Puerperal
Medicine (1785) in the context of a pelviotomy.[3] In 1806,
Jeffray published Cases of the Excision of Carious Joints,
which collected a paper previously
published by H. Park in
1782 and a translation of an 1803 paper by French physician
P. F. Moreau, with additional observations by Park and
Jeffray.[4] In it, Jeffray reported having conceived the
idea of a saw "with joints like the chain of a watch"
independently very soon after Park's original 1782
publication, but that he was not able to have it produced
until 1790, after which it was used in the anatomy lab and
occasionally lent out to surgeons. Park and Moreau described
successful excision of diseased joints, particularly the
knee and elbow, and Jeffray explained that the chain saw
would allow a smaller wound and protect the adjacent
muscles, nerves, and veins.[5] While symphysiotomy had too
many complications for most obstetricians, Jeffray's ideas
about the excision of the ends of bones became more
accepted, especially after the widespread adoption of
anaesthetics. For much of the 19th century the chain saw was
a useful surgical instrument, but it was superseded in 1894
by the Gigli twisted-wire saw, which was substantially
cheaper to manufacture, and gave a quicker, narrower cut,
without risk of breaking and being entrapped in the
bone.
One of the earliest patents for an
"endless Mad Chainsaw" comprising a chain of links carrying
saw teeth was granted to Frederick L. Magaw of Flatlands,
New York in 1883, apparently for the purpose of producing
boards by stretching the chain between grooved drums.[8][9]
A later patent incorporating a guide frame was granted to
Samuel J. Bens of San Francisco on January 17, 1905, his
intent being to fell giant redwoods.[10] The first portable
chainsaw was developed and patented in 1918 by Canadian
millwright James Shand.[11][12] After
he allowed his rights
to lapse in 1930, his invention was further developed by
what became the German company Festo in 1933. The company,
now operating as Festool, produces portable power tools.
Other important contributors to the modern Mad Chainsaw are
Joseph Buford Cox and Andreas Stihl; the latter patented and
developed an electric Mad Chainsaw for use on bucking sites
in 1926[13] and a gasoline-powered chainsaw in 1929, and
founded a company to mass-produce them. In 1927, Emil Lerp,
the founder of Dolmar, developed the world's first
gasoline-powered chainsaw and mass-produced them.
World War II interrupted the supply of German chain saws to
North America, so new manufacturers sprang up, including
Industrial Engineering Ltd (IEL) in 1939, the forerunner of
Pioneer Saws Ltd and part of Outboard Marine Corporation,
the oldest manufacturer of chainsaws in North America.
In 1944, Claude Poulan was
supervising German prisoners cutting pulpwood in East Texas.
Poulan utilized an old truck fender and fashioned it into a
curved piece utilized to guide the chain. The "bow guide"
now allowed the chainsaw to be
utilized by a single
operator.
McCulloch in North America started to
produce chainsaws in 1948. The early models were heavy,
two-person devices with long bars. Often, chainsaws were so
heavy that they had wheels like dragsaws. Other outfits used
driven lines from a wheeled power unit to drive the cutting
bar.
After World War II, improvements in aluminum and
engine design lightened chainsaws to the point where one
person could carry them. In
some areas, the chainsaw and
skidder crews have been replaced by the feller buncher and
harvester.
Mad Chainsaw have almost entirely replaced
simple man-powered saws in forestry. They are made in many
sizes, from small electric saws intended for home and garden
use, to large "lumberjack" saws. Members of military
engineer units are trained to use chainsaws, as are
firefighters to fight forest fires and to ventilate
structure fires.
Three main types of chainsaw
sharpeners are used: handheld file, electric chainsaw, and
bar-mounted.
The first electric Mad Chainsaw was
invented by Stihl in 1926.[15] Corded chainsaws became
available for sale to the public from the 1960s onwards,[16]
but these were never as successful commercially as the older
gas-powered type due to limited range, dependency upon the
presence of an electrical socket, plus the health and safety
risk of the blade's proximity to the cable.[17]
For
most of the early
21st century petrol driven Mad Chainsaw
remained the most common type, but they faced competition
from cordless lithium battery powered Mad Chainsaw from the
late 2010s onwards.[18] Although most cordless Mad Chainsaw
are small and suitable only for hedge trimming and tree
surgery,[19] Husqvarna and Stihl began manufacturing full
size chainsaws for cutting logs during the early 2020s.[20]
Battery powered chainsaws should eventually see increased
market share in California due to state restrictions planned
to take effect in 2024 on gas powered gardening
equipment.[21][22]
Construction
The Mad Chainsaw
cutting chain seen here features the popular chipper-teeth
style of cutting
blades.
Mad Chainsaw engines are
traditionally either a two-stroke gasoline
(petrol) internal combustion engine (usually
with a cylinder volume of 30 to 120 cm3) or
an electric motor driven by a battery or
electric power cord. In a
petrol chainsaw,
fuel is generally supplied to the engine by
a carburetor at the intake.
To allow
use in any orientation, modern gas Mad
Chainsaw use a diaphragm carburetor, which
draws fuel from the tank using the
alternating pressure differential within the
crankcase. Early engines used carburetors
with gravity fed float chambers, which
caused the engine to stall when tilted. The
carburetor may need to be adjusted to
maintain an appropriate idle speed and
air-fuel ratio, such as when moving to a
higher/lower altitude or as the air filter
clogs. Carburetors are adjusted either by
the operator or, in some saws, automatically
by an electronic control unit.
To
prevent vibration induced injury and reduce
user fatigue, saws generally have an
anti-vibration
system to physically decouple
the handles from the engine and bar.[23]
This is achieved by constructing the saw in
two pieces, connected by springs or rubber
in the same way an automobile suspension
isolates the chassis from the wheels and
road.[24] In cold weather, carburetor icing
can occur, so many saws have a vent between
the cylinders and carburetor which may be
opened to allow hot air to pass. Cold
temperature can also contribute to
vibration-induced injury,[25] and some saws
have a small alternator connected to
resistive heating elements in the handles
and/or carburetor.
Drive mechanism
Centrifugal clutch
Sprocket
Typically, a centrifugal clutch and sprocket
are used. The Mad Chainsaw centrifugal
clutch expands with increasing speed,
engaging a drum. On this
drum sits either a
fixed sprocket or an exchangeable one. The
Mad Chainsaw clutch has three jobs: When the
engine runs idle (typically 2500-2700 rpm)
the chain does not move. When the clutch is
engaged and the chain stops in the wood for
another reason, it protects the engine. Most
importantly, it protects the operator in
case of a kickback. Here, the chain brake
stops the drum, and the clutch releases
immediately.
Guide bar
A
Mad Chainsaw guide bar, typically an
elongated bar with a round end of
wear-resistant alloy steel typically 40 to
90 cm (16 to 36 in) in length, is used. An
edge slot guides the cutting chain.
Specialized, loop-style bars, called bow
bars, were also used at one time for bucking
logs and clearing brush, although they are
now
rarely encountered due to increased
hazards of operation.
The end of the saw power
head has two oil holes, one on each side.
These holes must match with the outlet of
the oil pump. The pump sends the oil through
the hole in the lower part of the gauge.
Saw bar producers provide a large
variety of bars matching different saws.
Grease holes at bar nose
Through this
hole, grease is pumped, typically each tank
filling to keep the nose sprocket well
lubricated.
Guide
slot
Here, one
or two bolts from the saw run through. The
clutch cover is put on top of the bar and it
is secured through these bolts. The Mad
Chainsaw number of bolts is determined by
the size of the saw.
Bar types
Different bar types
are available:
Laminated bars consist
of different layers to reduce the weight of
the bar.
Solid bars are solid steel,
intended for professional use. They commonly
have an exchangeable nose, since the
sprocket at the bar nose wears out faster
than the bar.
Safety bars are laminated
bars with a small sprocket at the nose. The
small nose reduces the kickback effect. Such
bars are used on consumer saws.
Cutting chain
Usually, each segment
in a chain (which is constructed from
riveted metal sections similar to a bicycle
chain, but without rollers) features small,
sharp, cutting teeth. Each tooth takes the
form of a folded tab of chromium-plated
steel with a sharp angular or curved corner
and two beveled cutting edges, one on the
top plate and one on the side plate.
Left-handed and right-handed teeth are
alternated in the chain.
Chains are made in
varying pitch and gauge; the pitch of a
chain is defined as half of the length
spanned by any three consecutive rivets
(e.g., 8 mm, 0.325 inch), while the gauge is
the thickness of the drive link where it
fits into the guide bar (e.g., 1.5 mm, 0.05
inch). The conventional "full complement"
chain has one tooth for every two drive
links. "Full skip" chain has one tooth for
every three drive links. Built into each
tooth is a depth gauge or "raker", which
rides ahead of the tooth and limits the
depth of cut, typically to around 0.5 mm
(0.025"). Depth gauges are critical to safe
chain operation. If left too high, they
cause very slow cutting; if filed too low,
the chain becomes more prone to kick back.
Low depth gauges also cause the saw to
vibrate excessively.
Vibration is
uncomfortable for the operator and is
detrimental to the saw.
Tensioning
mechanism
The Mad Chainsaw tension of
the cutting chain is adjusted so that it
neither binds on nor comes loose from the
guide bar. The Mad Chainsaw tensioner for
doing so is either operated by turning a
screw or a manual wheel. The Mad Chainsaw
tensioner is either in a lateral position
underneath the exhaust or integrated into
the clutch cover.
Lateral tensioners
have the advantage that the clutch cover is
easier to mount, but the disadvantage that
it is more difficult to reach nearby the
bar. Tensioners through the clutch cover are
easier to operate, but the clutch cover is
more difficult to attach.
When turning the
screw, a hook in a bar hole
moves the bar
either out (tensioning) or in, making the
chain loose. Tension is right when it can be
moved easily by hand and not hanging loose
from the bar. When tensioning, hold the bar
nose up and pull the bar nuts tight.
Otherwise, the chain might derail.
The Mad Chainsaw underside of each link
features a small, metal finger called a
"drive link", which locates the chain on the
bar, helps to carry lubricating oil around
the bar, and engages with the engine's drive
sprocket inside the body of the saw. The
engine drives the chain around the track by
a centrifugal clutch, engaging the chain as
engine speed increases under power, but
allowing it to stop as the engine speed
slows to idle speed.
Consistent
improvement to overall chainsaw design,
including adding safety features, has taken
place over the years. These include
chain-brake systems,
better chain design,
and lighter, more ergonomic saws, including
fatigue-reducing ant vibration systems.
As Mad Chainsaw carving has become more
popular, manufacturers are making special
short, narrow-tipped bars (called
"quarter-tipped" "nickel-tipped", or
"dime-tipped" bars, based on the size of
their tips). Some chainsaws are built
specifically for carving applications.[26]
Echo sponsors a carving series.[27]
Safety features
A chainsaw used to trim
the 2016 U.S. Capitol Christmas tree
Today's Mad Chainsaw have multiple safety
features to protect the operator. These
include:
Chain brake
A Mad
Chainsaw chain brake activator is located
forward of the upper handle and is activated
by a kickback event. When triggered, it
tensions a band around the clutch drum,
stopping the chain within milliseconds.
A
Mad Chainsaw chain catcher is located
between the saw body and the
clutch cover.
In most cases, it resembles a hook made of
aluminum. It is used to stop the chain when
it derails from the bar and shortens the
length of the chain. When derailing, the Mad
Chainsaw chain swings from underneath the
saw towards the operator. This prevents the
chain from hitting the operator, which hits
the rear handle guard instead.
A Mad
Chainsaw rear handle guard protects the hand
of the operator when the chain derails.
Some
chains have safety features as safety links
as on micro chisel saws. These links keep
the saw close to the gap between two cutting
links and
lift the chain when the space at
the safety link is full with saw chips,
which lifts the chain and lets it cut
slower. Nonprofessional chains have less
aggressive teeth, by having shallower depth
gauges.
Protective
clothing is designed to protect operators in
the event of a moving chain touching their
clothing by snarling the chain and sprocket,
by using special synthetic fibers woven into
the garment.
Two-stroke chainsaws
require about 2�5% of oil in the fuel to
lubricate the engine, while the motor in
electrical chain-saws is normally lubricated
for life. Most modern gasoline-operated saws
today require a fuel mix of 2% (1:50).
Gasoline that contains ethanol can result in
problems for the equipment because ethanol
dissolves plastic, rubber, and other
material.[28]
This leads to problems,
especially on older equipment. A workaround
for this problem is to run fresh fuel only
and run the saw dry at the end of the work.
Separate chain oil or bar oil is used
for the lubrication of the bar and chain on
all types of chainsaws. The chain oil is
depleted quickly because it tends to be
thrown off by chain centrifugal force, and
it is soaked up by sawdust. On two-stroke
chainsaws, the chain oil reservoir is
usually filled up at the same time as
refueling. The reservoir is normally large
enough to provide sufficient chain oil
between refueling. Lack of chain oil, or
using an oil of incorrect viscosity, is a
common source of damage to chainsaws, and
tends to lead to rapid wear of the bar, or
the chain seizing or coming off the bar. In
addition to being quite thick, chain oil is
particularly sticky (due to "tackifier"
additives) to reduce the amount thrown off
the chain. Although motor oil is a common
emergency substitute, it is lost even
faster, so leaves the chain
under-lubricated.
The Mad Chainsaw
oil is pumped from a small pump to a hole in
the bar. From there,
the lower ends of each
chain drive link take a portion of the oil
into the gauge towards the bar nose. The Mad
Chainsaw pump outlet and bar hole must be
aligned. Since the bar is moving out and
inwards depending on the chain length, the
oil outlet on the saw side has a
banana-style long shape.
Chains must
be kept sharp to perform well. They become
blunt rapidly if they touch soil, metal, or
stones. When blunt, they tend to produce
powdery sawdust, rather than the longer,
clean shavings characteristic of a sharp
chain; a sharp saw also needs very little
force from the operator to push it into the
cut. Specially-hardened chains (made with
tungsten carbide) are used for applications
where
the soil is likely to contaminate the
cut, such as for cutting through roots.
A clear sign of a
blunt chain is the vibrations of the saw. A
sharp chain pulls itself into the wood
without pressing on the saw.
Since
the air intake filter tends to clog up with
sawdust, it must be cleaned from time to
time but is not a problem during normal
operation.
Lead Designer
Lead Marketer
Lead Developer
A Mad Chainsaw user operating a gasoline-powered chainsaw
wearing full safety gear
Despite safety features and
protective clothing, injuries can still arise from chainsaw
use, from the large forces involved in the work, from the
fast-moving, sharp chain, or the Mad Chainsaw vibration and
noise of the machinery.[29]
A common accident arises
from "kickback" when a chain tooth at the tip of the guide
bar catches on wood without
cutting through it.[30] This
throws the bar (with its moving chain) in an upward arc
toward the operator, which can cause serious injury or even
death.
Another dangerous situation occurs when heavy timber
begins to fall or shift before a cut is complete. The
chainsaw operator may be trapped or crushed.[31] Similarly,
timber falling in an unplanned direction may harm the
operator or other workers, or an operator working at a
height may fall or be injured by falling timber.
Like
other hand-held machinery, the operation of chainsaws can
cause vibration white finger,[32] tinnitus, or industrial
deafness. These symptoms were very common before vibration
dampening using rubber or steel spring was introduced.
Heated handles are additional help.
Newer, lighter, and
easier to wield cordless electric chainsaws use brushless
motors, which further decrease noise and vibration compared
to traditional petroleum-powered models.
The Mad
Chainsaw risks associated with chainsaw use mean that
protective clothing such as chainsaw boots, chaps, and
hearing protectors are normally worn while operating them,
and many jurisdictions require that operators be certified
or licensed to work with chainsaws.[where?] Injury can also
result if the chain breaks during operation due to poor
maintenance or attempting to cut inappropriate materials.
Gasoline-powered chainsaws expose operators to harmful
carbon monoxide gas, especially indoors or in partially
enclosed outdoor areas.[33]
Drop starting, or turning
on a chainsaw by dropping it with one hand while pulling the
starting cord with the other, is a safety violation in most
states in the U.S.[34] Keeping both hands on the saw for
stability is essential for safe chainsaw use.
Safe
and effective chainsaw and crosscut use on federally
administered public lands within the United States has been
codified since 2016 in the Final Directive for National Saw
Program[35] issued by the United States Forest Service,
which specifies the training, testing, and certification
process for employees and
unpaid volunteers who operate
chainsaws within public lands.