Chainsaws: Getting to Know Your Chain
As a chainsaw owner or operator, it’s important to know your chainsaw’s chain. With terms flying around like pitch, gauge, round-tooth, square-tooth, chisel, full-complement, half-skip, and full-skip it’s easy to become confused. Let’s start with learning the anatomy of saw chain.
Every chain is made of links; your saw’s chain has three types: cutting teeth, drive links, and tie straps. Your chain’s cutting teeth are the “business” end of the chain; these do the cutting or chipping when you cut with your saw. These cutting teeth come in different varieties which are referred to as different cutting tooth profiles. The next type of link found in your chain is the drive link. The drive links travel inside the groove on your chainsaw’s guide bar while the drive sprocket makes contact with the tang of the links. This is what propels your saws chain around your guide bar. It’s important to make sure your chain’s gauge is compatible with your guide bar’s groove width. The tie straps are the links that attach the cutting teeth and the drive links together. They don’t have cutting teeth or the tang of the drive links, these links just hold the chain together. A tie strap with preset rivets is called a preset tie strap, the other half that just has rivet holes is referred to as a tie strap. Depending on your chain’s cutting tooth spacing there may be more or less of these in your chain.
Typically speaking, consumer chainsaws come with round-tooth profile chains. These chains are less prone to kickback and vibration. They can handle a more versatile work load. Kickback is a strong thrust of the saw back towards the sawyer because of improperly using the top corner of the guide bar’s nose. These chains scoop wood out of a cut and are best suited for removing tree limbs, clearing brush, stumping, and cutting through frozen or dirt- and mud-covered wood or hardwoods. These chains require more effort from the engine when making big cuts and are best applied to shorter bars. Most professionals, however, use square-tooth, or chisel profile chains. These chains chip the wood away, severing the wood fiber faster, and are best applied to longer bars (usually 24”+). There is no consensus as to which tooth profile is better as they serve different purposes and do different jobs more effectively.
Pitch and gauge are measurements used to describe the size of your chain. Pitch refers to the spacing between the rivets holding the chain links together. This is measured as fractions of an inch (1/4) or in thousandths of an inch (.404) and is calculated by taking the distance between any three consecutive rivets and dividing it by two. The numbers increase as the chains size increases. Gauge refers to the width of the chains drive teeth. This is measured in thousandths of an inch (.063). These measurements are mainly used as a reference to the chain’s compatibility with your saw’s guide bar and drive sprocket. You must match exactly the guide bars groove width and your chains gauge. If these numbers don’t match, the chain won’t have the correct clearance to rotate around your guide bar.
Tips from the mechanics: Always write down and keep these measurements in a place where you can easily access them for reference. When replacing your chain, it’s important to use a chain with measurements compatible with your guide bar and drive sprocket.
When we’re talking about full-complement, half-skip and full-skip, we’re talking about the spacing between the cutting teeth on the chain. A full-complement chain has the maximum number of teeth possible. These are the chains that are typically used on consumer equipment with a round-toothed profile. The benefits of these chains can also be considered their weaknesses. By having as many cutting teeth as possible these chains make smooth and clean cuts and respond more predictably to user input. These clean smooth cuts are the result of the saw cutting slower, as the close set teeth are pulling more debris out of the cut. But the tradeoff with the slower, smoother cut is increased engine strain.
Half-skip chains add a spacer or non-toothed link between pairs of cutting teeth and full-skip chains add two of these spacers which ends up reducing the number of teeth by approximately 1/3. A half-skip chain installed on a longer bar makes a rougher cut, but it cuts faster and easier through denser wood.
Half-skip chains tend to be a rare choice as replacement chains. Most occasional users tend to replace their full-complement chains with similar or identical full-complement chains, and most professionals prefer full skip chains. This leaves the half-skip replacement chains in the limbo of neither, consumers or professionals, wanting to experiment with this middle ground option.
At the end of the day, it’s important to remember the pitch and gauge of your original chain and to consider what types of cutting you plan on doing with your saw when choosing your replacement chain. You’ll want to keep a record of the pitch and gauge from your saw’s original chain, as you’ll want to find a replacement with the same measurements to fit your saw’s guide bar. Deciding what types of cutting tasks you’ll be performing with your chainsaw will help you decide which saw tooth profile and cutting tooth spacing is best for your saw and its intended work load.