Originally, chainsaws were used primarily by loggers. But since the introduction of small, light models, including an electric version, the chainsaw has become a common household tool. Chainsaws can be used to cut firewood, to buck up (to cut wood into usable lengths) scrap wood in the backyard, and to prune trees. Special attachments can turn a chainsaw into a brush cutter, a hedge trimmer, a powerful winch, or a posthole digger.
A chainsaw, whether gas-powered or electric, has several major components: The engine to provide power; the clutch and drive sprocket to transfer the power; and the chain and guide bar that, together, form the cutting mechanism.
Chainsaws are sized primarily according to the length of the guide bars, which range from an impractical 8 inches long to the specialized 60-inch bar for bucking huge logs.
The two-cycle engines are rated by cubic-inch displacement, rather than by horsepower. Displacement is a formula involving the distance the piston moves on the stroke, the size of bore for the piston, and how much fuel-air mixture the piston compresses on its upward stroke. Thus, it is an indicator of power—the greater the displacement, the greater the power. For these tools, displacement varies from just 1.6 cubic inches on a mini-saw to 8.3 cubic inches on large production saws.
Parts of a Chain
A chain has several distinct parts, all linked together, the most important of which is the cutter head that slopes back slightly to reduce friction drag when moving through wood. Directly in front of the cutter (and part of the same link)is the depth gauge, which keeps the cutter from biting too deeply into the wood. Between these two elements is the gullet, which catches and removes the sawdust. The correct height relationship between the cutter and the depth gauge is critical to a chain that cuts properly. Repeated sharpening causes the cutter to become shorter. When it does, the depth gauge must be filed down correspondingly.
The cutters normally are located on every other link, with the cutting edges facing in alternate directions. The cutting links are connected to each other by the drive links, which have hooked tangs that ride in the bar channel. The drive sprocket engages these tangs to turn the chain. Although the hooked part of the tang seems to be caught by the drive sprocket, it isn’t—rather, the hook faces forward and is designed to keep the groove clear of sawdust.
There are four basic types of cutters. The rounded chipper tooth is most common. It can easily be sharpened with a round file.
The chisel tooth is much more efficient. It is square on top rather than round. This type is used most often by professionals; weekend cutters find it hard to do the more precise sharpening it requires.
The semi-chisel tooth is used on the average-quality saw with increasing frequency This tooth design is a compromise between the chipper and the chisel tooth, and, like the chipper, the semi-chisel tooth can be sharpened with a round file.
The last type of tooth doesn’t have a special name, but it is specifically for saws that have automatic sharpeners. Hand sharpening must be done in addition to the automatic sharpening and this hand sharpening is difficult to do correctly. Also, this type of chain is more expensive than the others.
The Guide Bar
The guide bar is what keeps the chain moving straight and smoothly. It is made of hardened steel to resist the great amount of wear it receives from the chain. The tip of the bar is where most of the friction and resulting wear are centered. It is either made of specially hardened steel or protected by a nose sprocket that turns with the chain, reducing wear at that point. The bar is grooved all the way around the edge; the sides of these grooves are called rails. The drive links of the chain ride on top of the rails, kept in place by the tangs in the channel.
What to Look For
First decide whether you want electric or gas. The electric saws are considerably cheaper, quieter, and easier to maintain, since there is no complex engine to look after. However, their bar lengths tend to be short (8 to 16 inches), which generally limits them to light work around the yard. To cut a lot of firewood, you need a gas-engine chainsaw. A practical two-cycle gas-engine chainsaw has an engine with a 2.5 to 4.5-cubic-inch displacement and a 14- to 20-inch-long cutting bar.
There is a correlation between the size of the engine and the length of the cutting bar. The longer the bar, the bigger the engine must be in order to drive the chain effectively. The bar should be long enough to cut through most of the wood in only one pass. You can still cut larger logs by making two cuts, one from each side.
Modern chainsaws have several features that are worth insisting on. They are, in general order of priority, the following.
Solid-State Ignition Increasingly, chainsaws are being made with solid-state ignition, which means that you don’t need to periodically change the breaker points and condenser. This, in turn, means a big savings for you in time and effort.
Chain Brake The brake is built into the forward handle and must be cocked before using. If the nose of the bar catches an obstruction and is flung up at your face, the jolt against the front handle activates the brake.
Tip Guard This device actually prevents saw kickback by enclosing the nose of the bar with a steel guard.
Antivibration Device Rubber shock absorbers called antivibration cushions are another common feature found on chainsaws. These devices reduce the vibration of the saw that would otherwise be transmitted to you.
Automatic Oiler All good saws should have an automatic oiler. Because the oiler is geared to the engine speed, the faster the saw runs, the more oil it puts on the chain to reduce friction. The best system is an automatic oiler plus a manual override (pushing a small plunger with your thumb engages the override) because often the saw needs a little more oil than the automatic feed gives out.
Nose Sprocket Look for a saw with a sprocket in the nose of the guide bar. The sprocket turns with the chain to markedly reduce friction at that point. These sprockets must be kept greased.
Compression Release A particularly useful addition, especially on the larger saws, is a compression release button. This button releases the compression that builds up in the engine as you pull the starter rope, making it easier for the engine to start.
There are 3 main categories of chainsaw: electric, gasoline, and production models.
These saws are mostly classified as mini saws, but they also include light-duty models. They have bars that range from 8 to 16 inches long, with correspondingly larger motors for the longer bars. Since the cutting teeth tend to be smaller than on gas-engine saws, the cutting efficiency is reduced.
However, electric saws cost less than gas-powered saws. They are also quieter, as well as easier to start and maintain. They do well at cutting up small logs, cutting heavy brush, or pruning tree limbs. As with all electric tools, however, your mobility is limited to areas within reach of a power outlet.
If you plan to cut one or more cords of wood for your fireplace each year, either a light-or medium-duty saw is a wise choice. Both are light, portable, and powerful. Choose the size that’s best for you on the basis of how much and what size wood you plan to cut.
Power, which is determined by the engine’s displacement, ranges from 2.5 to 4.5 cubic inches. Most of these saws can accept two to three different bar lengths, depending on the size of the engine. Bar lengths range from 12 inches on the smallest variety to 20 or 25 on the large models. For most cutting needs, a bar between 14 and 20 inches is sufficient.
Most of the new saws are equipped with two extremely useful accessories: a chain brake and guard for safety, and an automatic oiler, plus a manual override for extra oil when needed.
If you plan to cut a lot of firewood or build your own log cabin, you will need a production saw. These range in power from 4.5 cubic inches to more than 8 cubic inches, but a 6-cubic-inch engine will more than do for anyone who isn’t a professional logger.
The bars on these saws usually run from 20 to 36 inches; a 25-inch bar is sufficient for most needs. On the larger saws, use a semi-chisel or chisel tooth chain for best cutting results. You can sharpen the chain by hand expertly on your own if you use a clamp-on file guide and a bevel-edged file. Most of these saws are now made with a chain brake, an automatic oiler plus manual override, and a solid-state ignition.