At some point there will come a time when your chainsaw chain is too worn to sharpen any further and needs to be replaced completely - the same is also true of the chainsaw sprocket and guide bar.
But how do you know when to replace your chainsaw saw chain, sprocket or guide bar?
Here we highlight some of the key points to consider when deciding if your chainsaw components are up for retirement...
When to replace a chainsaw chain
Wear markers
Every tooth on a Stihl chain will feature a number of wear markers, shown below in red. Sharpening the tooth and filing the depth gauge wears away at the steel and chrome plating, gradually reducing the size of the tooth. Once the wear markers have been met it’s essential to replace the chainsaw chain. Filing past the wear marker will greatly reduce the chain’s cutting performance, and increases the risk of the tooth breaking off.
Ideally you should reach the tooth and depth gauge markers at roughly about the same time. If this isn’t the case, you may inadvertently have sharpened the chain incorrectly, which can change the depth gauge setting and lead to either increased vibration or reduced cutting performance. Stihl's 2-in-1 EasyFiles automatically maintain the perfect depth gauge setting, helping to make sure your chain lasts as long as possible.
A wear marker is also present along the underside of the tooth, above the ‘toe’ and ‘heel’. If the chain is run without bar oil, or is tensioned too tightly over long periods, the extra friction will lead to premature wear to the bottom part of the tooth. You should immediately replace the chain if you notice this wear marker has been met.
Damaged or missing teeth
Hitting an unexpected nail or rock has the potential to cause serious damage to a chainsaw chain. It’s important that all the teeth on a chain are uniform length to prevent increased vibration and the chain ‘snatching’ mid cut. If the damage has significantly shortened or broken a number of teeth, it may not be practical to sharpen all the teeth to a uniform length so a new chainsaw chain is needed. 
When to replace the chain sprocket
Hidden behind the sprocket cover, the chain sprocket is the driving force behind the chain. As you’d expect the sprocket is subject to normal wear, so we recommend checking its condition at regular intervals using a control gauge. This can be used on both rim and spur sprockets featured on any petrol or cordless chainsaw or pole pruner so it’s definitely worth having in the back pocket!
The chain sprocket must be replaced if the depth of the wear marks reaches about 0.5mm, i.e. the wear limit. A seriously worn chain sprocket can cause the chainsaw chain and guide bar to wear at an increased rate, as well as reducing cutting performance too, so it’s important to keep an eye on.
When to replace your guide bar
Rail wear
Over time, the rails of the guide bar (the sides shown in this picture) can wear away, reducing the groove depth (or in other words, the amount of room left for the drive links to sit in). If the groove depth is too small, the tips of the drive links will scrape along the bottom and drastically impact how smoothly the chain moves around the guide bar. Turning the guide bar over can also help to wear both sides evenly and further extend the working life of the bar. 
Guide bars can last the lifespan of 4 chains, so this isn’t a problem Stihl chainsaw users should encounter regularly, but if you have noticed some wear to the rails, check the groove depth using the tip of the depth gauge tool found in the Stihl filing kits. If the groove depth is less than the minimum listed in the table below, it’s definitely time for some guide bar themed retail therapy.
It's time to replace your guide bar if the groove depth is less than the minimum
Guide bar damage
It’s possible that guide bars that have been damaged, pinched, splayed, chipped or unevenly worn can be repaired. So, unless your guide bar has been bent beyond reasonable repair, if your guide bar is still relatively new we’d recommend that you speak to our Service Team about a repair before asking about a replacement.
Don’t forget that Stihl chainsaws have been designed to work perfectly in combination with the recommended guide bar and chainsaw chain so whenever you need a new spare part, come and speak to Balmers GM as we are a Stihl Approved Dealer for official Stihl parts.