Although the modern chainsaw is associated primarily with forestry, it was originally developed as a surgical instrument. During the nineteenth century, chainsaws saw extensive use by orthopedists to excise diseased bone.The medical chainsaw was eventually replaced by more efficient surgical instruments, but in the 1920s, manufacturers began to produce electric and gasoline-powered chainsaws suitable for felling trees.
Today, Chainsaws have almost completely supplanted simpler man-powered saws in forestry. Activities such as tree felling, pruning, and bucking make extensive use of chainsaws, and tree surgeons use these powerful machines to remove branches and foliage. Specialized chainsaws with industrial-grade diamond teeth can even cut through concrete. Furthermore, many homeowners use chainsaws for a variety of landscaping tasks on private property.
Chainsaws are fairly complex devices that rely on many components to operate safely and efficiently. To find the right chainsaw for a given job, it is necessary to take all of these parts into consideration.
1. Saw Chain
The chainsaw's namesake component, the saw chain, is the part of the machine that actually cuts into wood. When the chainsaw is in operation, the motor propels the saw chain around a guide bar at high speeds, allowing the teeth to cut chips from the side and bottom. Somewhat counter-intuitively, modern saw chains feature depth gauges that limit the depth of cut on each individual tooth. Making sure that individual teeth do not bite too deeply into the wood stops the chain from binding in the wood and allows efficient, safe operation of the tool.
When shopping for a chainsaw, one of the most important components to consider is the tooth design. Some chainsaws feature full chisel chains with square cornered teeth; these teeth split wood fibers very easily and make quick work of softer woods. Other chainsaws use semi-chisel chains with rounded teeth. While these chains cannot match the performance of full chisel chains on softer woods, they maintain their cutting sharpness for longer periods of time. This type of chain is ideal for cutting into hard wood, dirty wood, frozen wood or tree stumps, which would cause full chisel chain to rapidly lose its edge.
Different saw chains also feature different arrangements of teeth. The full complement arrangement, also known as full house or standard chain, places one drive link between each pair of cutters. The full skip arrangement, in contrast, places two drive links between each pair of cutters. The semi-skip arrangement is a combination of the two. Full complement chains have more teeth than either of the other arrangements and thus require more sharpening time and more power to operate; however, they tend to produce smooth cuts and very fine sawdust. Arrangements with fewer teeth require less sharpening and less power to operate, but they tend to produce rougher cuts and thicker sawdust. It is also worth noting that full skip chains should only be used with larger chainsaws.
2. Power Source
Many chainsaws intended for home use run on electric power rather than gasoline. Cordless chainsaws tend to be small, portable, easy to use and relatively quiet. Though they have far less power than the other varieties, these chainsaws are perfect for smaller jobs at private residences. Larger electric chainsaws, which must be plugged in, are ideal for more extensive work. They tend to still be fairly light and have an advantage in terms of safety: Since there is no power source if the cord is unplugged, there is no risk that the machine will accidentally activate.
For larger, professional jobs, the best choice is a gasoline-powered chainsaw. These powerful machines make quick work of tree trunks and large branches. Because of the added weight from the fuel tank, though, gasoline-powered chainsaws are somewhat awkward to handle and can be especially dangerous in the hands of an inexperienced operator. Fortunately, the lack of a power cord makes the machine more portable and eliminates the risk of tripping.
3. Guide Bar
A chainsaw's guide bar is a long, rounded piece of metal, usually made from a wear-resistant steel alloy. Guide bars typically range from 16 to 36 inches long. An edge slot around the outside of the bar guides the cutting chain and holds it in position. The operator controls the machine by positioning the guide bar against the object he wishes to cut. Previously, loop-style guide bars known as bow bars were used to buck logs and clear brush, but they are now almost never used due to their increased risk of injury.
The chainsaw's throttle controls the supply of fuel to the engine and thus controls the saw's revolutions per minute. Thus, the throttle allows the chainsaw's operator to increase or decrease the saw's speed as necessary to adapt to different jobs. As a safety mechanism, modern chainsaws automatically stop the chain as soon as the operator releases pressure on the throttle.
Modern chainsaws also include throttle interlock locking mechanisms. If the interlock is not depressed, the throttle will not engage. This is another safety measure intended to prevent the machine from starting accidentally.
5. Engine Control
The engine connects to the cutting chain itself by means of a clutch and a sprocket. Among the clutch's functions is to keep the engine from stalling if the chain abruptly slows or stops, a fairly common occurrence when cutting through hard or frozen wood. Another is to prevent the chain from rotating while the engine is idling, preventing accidental damage to the saw or injury to the operator. A well-tuned clutch keeps the machine running efficiently and consistently, improving safety and performance.
Modern chainsaws feature a weighted wheel, called a flywheel, that stores rotational energy to keep the engine running at a consistent speed. The flywheel also plays a role in keeping the engine cool and preventing overheating.
6. Decompression Valve
As its name implies, the decompression valve releases air compression produced by operating the saw. Eliminating this compression makes starting the chainsaw much easier. It reduces the energy required to pull the starter cord, makes a strong ignition spark, and produces an ideal air-fuel mixture in the engine.
7. Noise Control
Because they operate at very high speeds, chainsaws tend to produce a lot of noise. In particular, larger chainsaws with gasoline-powered engines tend to be extremely noisy devices. Mufflers work to at least somewhat reduce the noise output; they not only keep the operator's neighbors happy but also help the operator himself stay aware of his surroundings, thereby improving safety. Note that smaller electric chainsaws naturally make less noise and thus require less noise control.
Most jurisdictions also recommend that operators wear ear defenders or ear plugs to reduce noise to levels that will not cause hearing damage.
8. Chain Stoppers
Given their impressive cutting power, chainsaws are potentially very dangerous devices. As such, chainsaw manufacturers are required to include multiple components designed to reduce the risk of an accident. One of these devices is the chain catcher, a metal or plastic guard designed to intercept a broken or derailed chain. Instead of striking the operator's hand, the chain should simply hit the chain catcher. Likewise, since 1995 all chainsaws must include a chain brake, which immediately stops the chain from moving if kickback occurs. Although the chain brake cannot stop the chain from hitting the operator at all, it can stop the chain from rotating as it hits the operator.
It is important to note that these and other safety features are fairly recent innovations. For example, chain brakes have only been required since 1995. When searching for a chainsaw online, watch out for older chainsaws that may not include some of those features. Only experienced operators should even consider using chainsaws that do not have chain catchers and brakes.
9. Anti-Vibration Handle Systems
Even when they are lubricated well and used properly, chainsaws tend to vibrate a great deal. Excessive vibration can cause a variety of injuries to the operator, including white finger and hand-arm vibration syndrome. To reduce the stress this vibration places on the user's hands, modern chainsaws separate the actual cutting portion of the device from the handle and controls using a mounting system. Some chainsaws use metal springs to prevent vibration from reaching the operator, while others use rubber bushes.
Some modern chainsaws also include electrically heated handles. Although these devices do not cut down on vibration per se, they can help to prevent vibration-related injuries by encouraging circulation to the operator's fingers. Chainsaws with heated handles are particularly well-suited to cold-weather jobs.
10. Safety Features
A hand guard is a plastic shield that stands between the user's hands and the cutting chain in the event of kickback. In combination with a properly functioning chain brake and chain catcher, a good hand guard can do plenty to prevent the operator from being seriously injured.
A well-maintained chainsaw blade is sharp enough to cause injury even when the machine is not in use. During storage and transport, it is very important to cover the blade with a plastic scabbard. The scabbard also protects the blade itself from damage if it accidentally falls to the ground or bangs against a wall.
Choosing the Right Chainsaw
When purchasing a new chainsaw, safety is the first and most important consideration for inexperienced and experienced operators alike. Remember that older chainsaws may not have all of the safety features needed to prevent injury. While opting for an older, less safe chainsaw may seem like an easy way to save money on the purchase, the cost of a single trip to the emergency room will more than offset those savings. The best policy is to make sure that a chainsaw has all of the aforementioned safety features before purchasing it.
Second, it is important to pick the right chainsaw for the job. For instance, consider the type of wood to be cut and choose the right type of teeth to cut through that wood. Likewise, carefully consider the power source. Most homeowners will find that electric chainsaws can take care of all of their needs, but larger yards and bigger jobs may require gas-powered chainsaws to handle thick branches and tree trunks.
Although finding an affordable price is important when making any purchase, the cost should always be the last consideration when purchasing a chainsaw. It simply is not worthwhile to compromise on safety or suitability for the job to get a better deal. Remember that picking a chainsaw that is not suited for the task is also a safety risk.
When used properly, a chainsaw is a safe and efficient tool. Having all of the correct components in good working order goes a long way towards using a chainsaw safely and effectively. Whether you are purchasing an entire chainsaw or individual parts, it is important to understand the function of every component and select the best parts to get the job done.