The Stihl MS170 is a compact and powerful tool that makes light work of yard cleanup and small felling tasks, but its small size does not mean it should be treated with less respect than a professional saw. The most dangerous part of any chainsaw is a neglected or damaged chain. Because the MS170 operates at high chain speeds, any structural failure in the metal links or a loss of cutting control can lead to serious injury in a fraction of a second. Knowing how to identify an unsafe chain is a fundamental skill for every homeowner. While sharpening can fix a dull edge, there are certain types of damage that no amount of filing can repair. In these cases, the only safe option is to retire the chain and install a fresh, high quality replacement from a trusted brand like Stens or Trilink.
Recognizing Structural Damage to the Links
The chain on your Stihl MS170 is made up of dozens of individual components, including cutters, drive links, and tie straps, all held together by steel rivets. Over time, the stress of cutting through tough wood can cause these metal parts to fatigue. Structural failure is the most dangerous form of chain damage because it can lead to the chain snapping while under full load.
You should perform a close visual inspection of the chain and look for the following structural red flags:
- Cracked tie straps: Look for tiny hairline fractures in the metal plates that connect the cutters to the drive links.
- Loose or mushroomed rivets: If the rivets appear to be wobbly or the heads are worn down, the chain is at a high risk of flying apart.
- Peened or damaged drive links: If the bottom part of the link that sits in the bar groove is burred or smashed, it can catch on the bar rails and cause a sudden stop or derailment.
- Severe rust or corrosion: While surface rust can often be cleaned, deep pitting in the metal weakens the overall tensile strength of the chain.
If you notice any of these structural defects, the chain is no longer airworthy. A snapped chain can whip back toward the operator or wrap around the drive sprocket, causing extensive damage to the saw’s crankcase and pose a major safety risk.
Excessive Vibration and Inconsistent Cutting
A safe chainsaw chain should cut smoothly and predictably. If your Stihl MS170 has begun to shake violently or "bounce" against the wood as you try to start a cut, the chain has likely reached an unsafe state. This vibration is often caused by uneven cutter lengths or damaged depth gauges, also known as rakers.
When a chain is sharpened improperly, one side of the chain may be cutting deeper than the other. This creates an imbalanced load that pulls the saw to one side. Other signs of a lack of control include:
- The saw "kicking" back toward you even when you aren't using the nose of the bar.
- The chain grabbing or jerking during a cut rather than pulling smoothly through the timber.
- Heavy sawdust instead of wood chips, which forces the operator to apply dangerous amounts of downward pressure.
- The chain jumping out of the bar groove frequently despite having the correct tension.
Applying excessive force to a dull or damaged chain is a leading cause of accidents. A chain should do the work for you. If you find yourself leaning your body weight into the saw to make progress, your chain is unsafe and needs to be replaced with a precision ground option from Trilink or Stens.
The Dangers of "Heat Stretched" Chains
Heat is a natural byproduct of friction, but if your Stihl MS170 isn't receiving enough bar oil, the chain can overheat to the point of permanent damage. When steel gets too hot, it undergoes a process called heat stretching. This is not the normal stretch that occurs with a new chain, rather, it is a permanent deformation of the metal links and rivets.
A heat stretched chain is unsafe because it can no longer maintain proper tension. You may find that you tighten the chain, but after only thirty seconds of cutting, it is hanging off the bar again. This constant sagging increases the likelihood of the chain jumping the bar and striking the operator’s hand or leg. Furthermore, extreme heat can make the steel brittle. If you see blue or dark purple discoloration on the cutters or drive links, the metal’s temper has been ruined, making it prone to shattering upon impact with a hard knot or a frozen log.
Worn Out Cutters and Depth Gauges
Every chainsaw cutter has a "witness mark" etched into the top of the tooth. This line serves as a safety limit for sharpening. Once you have filed the tooth back to this line, the cutter has become too small to maintain its structural integrity. A tooth that is filed beyond this point can break off during a cut, becoming a high speed projectile.
Similarly, the depth gauges (the rounded bumps in front of each cutter) must be maintained at the correct height. If the depth gauges are filed too low, the cutter will take too big of a "bite" out of the wood. This is a primary cause of aggressive kickback. If your chain looks like the teeth have been filed down to tiny stubs, or if the depth gauges have been lowered excessively to compensate for a dull edge, the chain is a safety hazard. Replacing the old chain with a Stens or Trilink low kickback chain from xtremeope.com is the best way to restore the safe handling characteristics of your Stihl MS170.
Checking the Fit and Gauge
An often overlooked safety issue is using a chain that is not perfectly matched to the guide bar of the MS170. Stihl uses specific gauges, most commonly 0.043 inch or 0.050 inch, for their small saws. If a previous owner installed the wrong gauge of chain, it may feel "sloppy" in the bar groove. A chain that can tilt too far to the left or right is prone to climbing out of the bar, especially during a bore cut or when the bar is under a twisting load. Always verify that your replacement chain matches the specifications stamped on the side of your Stihl guide bar.
Frequently Asked Questions
Can I remove a few links to fix a stretched chain? No, this is a very dangerous practice. If a chain has stretched so much that the tensioner can no longer take up the slack, the metal has been structurally compromised. Removing links to "shorten" the chain does not fix the weakened rivets and tie straps, it only hides the symptom of a failing chain.
What is kickback and how does the chain affect it? Kickback occurs when the chain at the tip of the bar catches on the wood and throws the saw upward toward the operator. Chains with aggressive, high depth gauges or damaged cutters are much more likely to cause kickback. Low kickback chains from Trilink and Stens are designed with safety links to reduce this risk.
Is it safe to use a chain that has hit a rock? If a chain hits a rock or a nail, you must stop immediately and inspect it. While a light touch may just dull the teeth, a hard impact can crack the cutters or the tie straps. If you see any chipped or missing pieces of metal on the cutters, the chain should be replaced.
How do I know if my chain tension is correct? A correctly tensioned chain should be snug against the bottom of the bar, but you should still be able to pull it around the bar by hand. If you can pull the drive links completely out of the bar groove with two fingers, the chain is too loose and is at risk of jumping.
Why does my chain get loose as I cut? It is normal for a chain to expand as it gets warm. However, if it becomes excessively loose very quickly, it is either a sign of poor lubrication or that the chain is "heat stretched" and is failing structurally.
Prioritizing Your Safety on the Job
The Stihl MS170 is a fantastic tool for maintaining your property, but its efficiency should never come at the cost of your safety. Developing the habit of inspecting your chain before every use is the best way to prevent accidents before they happen. If you notice cracks, excessive stretch, or signs of improper sharpening, do not take the risk of "one last cut." A high quality replacement chain is a small price to pay for the peace of mind that comes with knowing your equipment is safe and reliable. To find a durable, high performance Trilink or Stens chain that is a perfect fit for your Stihl MS170, visit the experts at XtremeOpe.com today.
Related Articles
- Why Chainsaw Chains Dull Quickly on a Stihl MS170 (And When It's Time for a Replacement) – Discover what causes rapid chain wear and how proper maintenance can help extend cutting performance.
- Stihl MS170 Chainsaw Chain Size Guide: Pitch, Gauge, and Drive Links Explained – Learn how pitch, gauge, and drive link count work together to ensure a proper chain fit.