Before replacing a chain it's important to be able to identify when a chain needs to be replaced as to when it can just be sharpened. Oftentimes, if your chainsaw is not cutting as quickly as it should, sharpening the chain is a more affordable option than replacing it. A sharp chain ensures a consistently proper cut, protects the chainsaw from additional wear, and reduces the likelihood of kickback occurring which is one of the most common chainsaw injuries. There are many factors that affect a chain's life: the type of wood you're cutting- hardwood will wear a chain out faster than softwood; a full chisel chain will wear faster than a semi-chisel chain; low bar oil will cause early wear; heavy extended use wears faster than light pruning.
When to sharpen a chain?
If you notice your cuts are throwing out finer sawdust rather than coarse chips
you find you have to apply more pressure into the saw when cutting.
there's an excess of smoke coming from the saw despite proper chain oil level and fuel mixture.
you're constantly having to adjust the chain tension.
If your chainsaw experiences these symptoms then the chain needs to be examined to check for potential damage. If there's no evident chain damage then sharpen the chain using the correct specified file gauge for your chain and filing angle.
Check out our article on how to properly sharpen your chainsaw chain.
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How do I know my chain needs to be replaced?
damaged cutter teeth
the chainsaw feels unbalanced when cutting (pulling to one side).
cuts are crooked.
chain rakers are too worn down causing an uneven depth gauge across the chain. (see illustration below)
Note: The above image illustrates a common depth gauge measurement on many Oregon chains. This height distance between the raker (the front of the chain marked 25 in the image) is important as this height determines the amount of wood severed by the cutter tooth. Some people may feel tempted to file the rakers below specifications to compensate for a dull chain. This is not the correct practice as a lower depth gauge will cause the saw to overwork itself and makes it more prone to kickback.
What measurements are needed to find the correct replacement chain?
There are three measurements used to identify the correct replacement chain- gauge, pitch, and amount of drive links. It's imperative for these specifications to match otherwise damage can be done to the saw and injury can occur to the user. If the incorrect chain is used the chain can skip off the bar causing injury, and damage to the chain, sprocket, and bar of the chainsaw. These chain measurements can often be found stamped along the side of your chainsaw bar.
Chain pitch is defined as the total distance between three rivets of the chain divided in half. There are different chain pitches used depending on the power output of the saw and the bar application. The most common chain pitches are 1/4", .325", 3/8", 3/8" low-profile (also called ’91’ by Oregon and ‘Picco’ by Stihl), and .404". The 3/8" low-profile chain measures a 3/8" pitch but the chain has a narrower kerf for more power-efficient cutting. For this reason, typically, a 3/8" low-profile chain is faster than a 3/8" chain since the narrower kerf displaces a smaller amount of the material being cut, therefore requiring less power. 3/8" low-profile chains are often equipped on 50cc and lower chainsaws with up to an 18" bar. If your chainsaw came equipped with a 3/8" low-profile chain it's best to continue using the specified chain instead of a 3/8". Installing a 3/8" chain on a saw that's best suited for a 3/8" low-profile chain will result in suboptimal performance. Also, it is not advised to mix a 3/8 Lo-profile chain onto a standard 3/8 clutch sprocket and vice versa. Not only do you need to match the chain pitch to the stated pitch of your bar, but you need to ensure the pitch of the chain you are using matches the pitch of your clutch sprocket.
The drive link measured width is what's referred to as the chain gauge. The most common chain gauge types are .043", .050", .058", and .063". The chain gauge must match the gauge of the bar or else the chain won't sit properly inside of the bar's groove. This can result in the chain damaging the bar, burring the chain's drivers, and possible injury. The gauge of a chain is determined by the power output of the saw and the bar length. A wider gauge is more durable but adds extra weight which can reduce cutting speed. Manufacturers will tend to balance the weight to durability aspect when they design bars for their chainsaw models.
Chain Drive Links
The chain driver is the bottom component of the chain that travels inside the groove of the chainsaw bar while the tang of the driver makes contact with the bar sprocket. The size of your chain is determined by the total number of drive links. The total drive links must match the drive links specified for the bar otherwise the chain will be too large or too short. This can be a mundane process but you should individually count the total drive links of a replacement chain before installing it on your chainsaw. There are multiple ways you can find out how many drive links are needed for your replacement chain: you can count the links, check the side of your bar for the total, or check the face of the drive links themselves. On some chains, there will be a number stamped into the face of the driver indicating the total drive links required for a replacement chain loop.
Now that you're able to identify the correct replacement chain for your chainsaw, what about the different types of chains out there?
What are the different types of chains?
There are a plethora of chain options available, some chain designs being better suited for certain applications than others. We will outline some of the common chain options below.
Regular Chains / Full Complement Chain
For most everyday applications the chain you'll be looking for is a skip tooth chain. Just as the name suggests, a skip tooth chain has one tie strap spaced between each cutting tooth. The single space between the cutter teeth creates a clearing for the woodchips, thus allowing for lower resistance. This chain cuts faster than a full skip on medium to small bars due to having more cutter teeth.
Full Skip Chain
A full-skip chain (aggressive chain) has two tie straps spaced between each cutting tooth. This style of chain is more commonly used on guide bars longer than 24" as it offers the least resistance. By having fewer teeth and more space for chips to clear, this chain produces less drag than a regular chain which means the chainsaw can run at a higher power curve. This is important for longer bars as the longer the bar the more teeth are used and the greater the need to clear chips as it builds up in wider logs. More teeth on the bar create additional load for the chainsaw's engine. The idea is to balance the number of teeth required for faster chain speeds and optimal chip displacement.
For any sawmill work, you exclusively want to use a ripping chain. Ripping chains are ground at a less aggressive angle than regular chiseled chains. When cutting parallel to the wood grain the shallow cutting angle of these chains allows for more precise, smoother cuts. The semi-chiseled design of these chains helps to prolong the chain's sharpness and makes it more resistant to damage. It's not recommended to use a ripping chain for anything other than milling as the chain cuts slower than the other options.
Full Chisel Chain vs Semi Chisel Chain
When we mention "chisel" we're referring to the profile of the cutter teeth. A full chisel chain has a more squared edge, making it more aggressive and a faster cutting chain, but it tends to dull faster and is more susceptible to kickback. A semi-chisel chain has rounded-corners making it cut slower, but it stays sharp longer and is easier to sharpen. A full chisel chain is a good choice for clean hardwood, while a semi-chisel chain is often the better choice for softer or dirty wood.