Saw chain
Encyclopedia
The saw chain, or "cutting chain", is a key component of a chainsaw
. It consists of steel links held together by rivet
s, and superficially resembles the bicycle
-style roller chain
, although it is closer in design to a leaf chain. Its key differences are sharp cutting teeth on the outside of the chain loop, and flat drive links on the inside, to retain the chain on the saw's bar and allow propulsion by the engine or motor.
Saw chains (and chainsaws generally) are used for cutting wood. This may be for harvesting trees for pulp or timber, for tree surgery, or for processing firewood.
Whether for hand-held chainsaws, mechanical timber harvesters
or chain mortisers, the saw chain has undergone dramatic development since its invention. Modern chains designed for high power, high-speed sawing applications will vastly outperform older designs, while allowing a far greater degree of safety and reliability in use.
by cutting chips from the side and bottom. In order to operate properly, the depth to which each tooth cuts must be limited to avoid it binding in the wood. Scratcher chain, like the teeth on a hand saw, simply uses a multitude of teeth to prevent individual teeth from sinking too far in without undue pressure on the bar. Chipper chain, and all subsequent designs, incorporate a depth gauge on each cutter link to limit depth of cut on each tooth. This has two distinct advantages over scratcher chain - it enables the use of fewer cutters per unit length of chain, which allows for shorter downtime for sharpening, and produces a more "open" chain layout, allowing far better clearance of chips and debris from the kerf. Individual depth gauges on each tooth also enable the use of skip chain. Skip or semi-skip chain has a further reduction in the number of teeth and is used for applications where much debris is produced, such as ripping or cross-cutting very large sections of wood. Skip chain also absorbs less power from the motor
per unit length of chain than full-complement chain, allowing the use of a longer bar/chain combination on any given motor.
Very early chainsaws used tooth configurations very similar to conventional hand saws. These were very simple saw teeth following a wave pattern (left, centre, right, centre) with no depth gauges as such, relying purely on bar pressure to limit the cutting rate. They were inefficient and slow in use, and were soon superseded by chipper chain. They required great skill and a lot of time to sharpen in the field leading to extended downtime between sessions.
Chipper chain invented by Joseph Cox
improved dramatically on the performance of scratcher chain. Chipper used a tooth that was curled over the top of the chain, with alternate teeth pointing left and right. Ahead of the tooth was a depth gauge, which allowed for good clearance around the tooth for chip clearing while limiting the depth of cut and preventing grabbing or overloading. Chipper chains are still available from Carlton and are sometimes used for dirty work, since their very large working corner allows the cutter to retain its effective sharpness for a long time in abrasive conditions.
For general use in forestry
, tree surgery and firewood
cutting, three basic configurations exist. Full chisel
chain has a square cornered tooth, splitting wood fibers easily in the cut for fast, efficient cutting in clean softwood
. Semi-chisel chain has a rounded working corner formed by a radius between the top and side plates. While slower than full chisel in softwood, it retains an acceptable cutting sharpness longer, making it the preferred choice for dirtier wood, hard
or dry wood, frozen wood or stump work, all of which would rapidly degrade full chisel chain. "Chamfer chisel" chains by Oregon are similar to semi-chisel design but have a small 45 degree chamfer between the plates rather than a radius. Performance is similar to good semi-chisel.
The key differences between semi-chisel and chipper chains are the size of the radius at the working corner. In cross-section a chipper tooth looks like a question mark, having a full radius over the whole cutting portion of the tooth, whereas a semi chisel design is more like a number "7" with the top-right corner slightly rounded.
alloys optimised for cutting in extremely cold conditions, chains with tungsten carbide
teeth for very dirty conditions and rescue work, ripping chains with altered blade geometry for making ripping cuts, and milling chains for chainsaw mill
s.
.
Large scale operators and retail shops may buy bulk chain on reels. This must then be cut and joined to length which is done by inserting rivet pins. These non-reusable pins are usually supplied already installed into a half-link and must be peened over against a half-link on the other side. As this peening is done with a bench-mounted rotary tool, rather than hammering, it is referred to as "rivet spinning". The tool is usually hand-cranked, or may be electrically powered for mass production.
Chainsaw
A chainsaw is a portable mechanical saw, powered by electricity, compressed air, hydraulic power, or most commonly a two-stroke engine...
. It consists of steel links held together by rivet
Rivet
A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...
s, and superficially resembles the bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
-style roller chain
Roller chain
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and simple machines like...
, although it is closer in design to a leaf chain. Its key differences are sharp cutting teeth on the outside of the chain loop, and flat drive links on the inside, to retain the chain on the saw's bar and allow propulsion by the engine or motor.
Saw chains (and chainsaws generally) are used for cutting wood. This may be for harvesting trees for pulp or timber, for tree surgery, or for processing firewood.
Whether for hand-held chainsaws, mechanical timber harvesters
Harvester (forestry)
A harvester is a type of heavy forestry vehicle employed in cut-to-length logging operations for felling, delimbing and bucking trees. A forest harvester is typically employed together with a forwarder that hauls the logs to a roadside landing.- History :...
or chain mortisers, the saw chain has undergone dramatic development since its invention. Modern chains designed for high power, high-speed sawing applications will vastly outperform older designs, while allowing a far greater degree of safety and reliability in use.
Principles of saw chain operation
Saw chains operate by being propelled around a guide bar, removing material from the kerfKerf
Kerf and similar can mean:* kerf, the width of a cut* Kerf, a poetry collection by Peter Sanger* Kerala E.N.T. Research Foundation , a hospital at Kollam in Kerala in India...
by cutting chips from the side and bottom. In order to operate properly, the depth to which each tooth cuts must be limited to avoid it binding in the wood. Scratcher chain, like the teeth on a hand saw, simply uses a multitude of teeth to prevent individual teeth from sinking too far in without undue pressure on the bar. Chipper chain, and all subsequent designs, incorporate a depth gauge on each cutter link to limit depth of cut on each tooth. This has two distinct advantages over scratcher chain - it enables the use of fewer cutters per unit length of chain, which allows for shorter downtime for sharpening, and produces a more "open" chain layout, allowing far better clearance of chips and debris from the kerf. Individual depth gauges on each tooth also enable the use of skip chain. Skip or semi-skip chain has a further reduction in the number of teeth and is used for applications where much debris is produced, such as ripping or cross-cutting very large sections of wood. Skip chain also absorbs less power from the motor
Motor
Motor is a device that creates motion. It usually refers to an engine of some kind. It may also specifically refer to:*Electric motor, a machine that converts electricity into a mechanical motion...
per unit length of chain than full-complement chain, allowing the use of a longer bar/chain combination on any given motor.
Scratcher teeth
Chipper teeth
Joseph Buford Cox
Joseph Buford Cox , invented what is now known as the chipper type chain for chain saws. He based his design on the C-shaped jaws of the larva of the timber beetle....
improved dramatically on the performance of scratcher chain. Chipper used a tooth that was curled over the top of the chain, with alternate teeth pointing left and right. Ahead of the tooth was a depth gauge, which allowed for good clearance around the tooth for chip clearing while limiting the depth of cut and preventing grabbing or overloading. Chipper chains are still available from Carlton and are sometimes used for dirty work, since their very large working corner allows the cutter to retain its effective sharpness for a long time in abrasive conditions.
Chisel and semi-chisel teeth
Forestry
Forestry is the interdisciplinary profession embracing the science, art, and craft of creating, managing, using, and conserving forests and associated resources in a sustainable manner to meet desired goals, needs, and values for human benefit. Forestry is practiced in plantations and natural stands...
, tree surgery and firewood
Firewood
Firewood is any wood-like material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form....
cutting, three basic configurations exist. Full chisel
Chisel
A chisel is a tool with a characteristically shaped cutting edge of blade on its end, for carving or cutting a hard material such as wood, stone, or metal. The handle and blade of some types of chisel are made of metal or wood with a sharp edge in it.In use, the chisel is forced into the material...
chain has a square cornered tooth, splitting wood fibers easily in the cut for fast, efficient cutting in clean softwood
Softwood
The term softwood is used to describe wood from trees that are known as gymnosperms.Conifers are an example. It may also be used to describe trees, which tend to be evergreen, notable exceptions being bald cypress and the larches....
. Semi-chisel chain has a rounded working corner formed by a radius between the top and side plates. While slower than full chisel in softwood, it retains an acceptable cutting sharpness longer, making it the preferred choice for dirtier wood, hard
Hardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
or dry wood, frozen wood or stump work, all of which would rapidly degrade full chisel chain. "Chamfer chisel" chains by Oregon are similar to semi-chisel design but have a small 45 degree chamfer between the plates rather than a radius. Performance is similar to good semi-chisel.
The key differences between semi-chisel and chipper chains are the size of the radius at the working corner. In cross-section a chipper tooth looks like a question mark, having a full radius over the whole cutting portion of the tooth, whereas a semi chisel design is more like a number "7" with the top-right corner slightly rounded.
Chain arrangements
There are also different arrangements of teeth on the chain.- "Full Compliment" chain has a left cutter, drive link, right cutter, drive link arrangement and is used for most applications.
- "Skip" has a left cutter, drive link, drive link, right cutter arrangement. It has 1/3 fewer cutting teeth and is generally used on long bars (24"+) for added chip clearance or when a bar longer than ideal for a given power head is used. Fewer teeth require less power to operate.
- "Semi-Skip" is a mixture of the previous two arrangements.
Chain specifications and dimensioning
Cutting chain comes in a large number of configurations, but these are reduced to a few key dimensions for replacement or specification purposes.- Gauge. The gauge of the chain is the thickness of the drive links, and is dictated by the gauge of the bar on which it is to be run. Usual gauges are .050" (1.3 mm) - .058" (1.5 mm) and .063" (1.6 mm). Chain and bar gauge must match; a chain that is too large will not fit, one that is too small will fall sideways and cut poorly.
- Pitch. The pitch of the chain is the average distance between two rivets. As the distance between rivets varies, the pitch can be measured by measuring between three rivets and dividing this distance by two. Usual pitches are 0.325", 3/8" and 0.404". 3/4" is used for harvester applications, and very rarely for handheld cutting. the pitch of the chain must match the drive sprocket, and the nose sprocket (if fitted).
- Length. A chain loop must be of an appropriate length in order to run safely. This is described by the number of drive links. This number is determined by the length and type of bar, the sprocket size and the overall configuration of the saw. For replacement purposes, simply count the drive links on the old chain.
Specialised chains
A number of very specialised chain types have emerged over recent years. These include chains made of steelSteel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
alloys optimised for cutting in extremely cold conditions, chains with tungsten carbide
Tungsten carbide
Tungsten carbide is an inorganic chemical compound containing equal parts of tungsten and carbon atoms. Colloquially, tungsten carbide is often simply called carbide. In its most basic form, it is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery,...
teeth for very dirty conditions and rescue work, ripping chains with altered blade geometry for making ripping cuts, and milling chains for chainsaw mill
Chainsaw mill
An Alaskan mill or chainsaw mill is a type of sawmill that is used by one or two operators to mill logs into planks for use in furniture, building and other types of timber construction....
s.
Joining chain
Chains are usually bought ready-joined to length, to suit a particular bar. All chainsaws have adjustable bar mounts to allow their chain tightness to be adjusted, allowing for any wear in the chain linkages. There is no requirement to remove links to shorten worn chains, chains will wear out on their cutting teeth before wear in their pivots becomes a problem. The adjustment also permits enough slack to allow a chain to be installed, so there is no need for a "split link" when fitting, as for bicyclesBicycle chain
A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics. Nickel also confers a measure of...
.
Large scale operators and retail shops may buy bulk chain on reels. This must then be cut and joined to length which is done by inserting rivet pins. These non-reusable pins are usually supplied already installed into a half-link and must be peened over against a half-link on the other side. As this peening is done with a bench-mounted rotary tool, rather than hammering, it is referred to as "rivet spinning". The tool is usually hand-cranked, or may be electrically powered for mass production.
See also
- Joseph Buford CoxJoseph Buford CoxJoseph Buford Cox , invented what is now known as the chipper type chain for chain saws. He based his design on the C-shaped jaws of the larva of the timber beetle....
, inventor of chipper saw chain. - Chainsaw safety featuresChainsaw safety featuresThis article is about risk control methods specific to chainsaws and chainsaw operations. Chainsaws incorporate numerous safety features common to many engine-driven power tools. Manufacturers have invented numerous design features to improve safety. Some features have become de facto standards,...
- Chainsaw safety clothingChainsaw safety clothingRegulations generally recommend that chainsaw users wear protective clothing, also known as Personal Protective Equipment or PPE, while operating chainsaws...