Why Does my Chain Keep Coming off my Chainsaw?

Chainsaws are great tools that can tackle some of the hardest pruning and brush-clearing tasks. Powerful tools can help us get our work done much faster but can also present a danger if they are not properly used and maintained. One of the most common problems chainsaw operators encounter is a loose chainsaw chain

While on-the-fly adjustments to a loose chain can restore proper tension, it may not be a long-term solution, especially if the chain keeps coming off. Letting your chainsaw chain slip into poor condition can damage your machine and injury you or those nearby. Read on to figure out why your chainsaw chains keep coming off and what you can do to not make the issue worse.

What is the Reason My Chainsaw Chain is Slipping Off?

There are a couple of reasons a chainsaw chain will come loose, and most happen under normal operation. If it only happens a single time, it was probably just improper tension from previous maintenance, but there are some common reasons why it happens repeatedly, and then long-lasting solutions are your best bet. If you have a loose chain, check for these issues to prevent a safety hazard.

The Chain Was Not Adjusted Properly

Husqvarna 581643603 X-Cut SP33G 18" Chainsaw Chain, Grey

Sometimes the last time the chain was adjusted, it wasn’t tightened correctly. Tighten the tension with the tension bolt or automatic tension handle if your mode has one. The chain should be loose enough to jiggle with your fingers but not slip off the drive links. If it does come off the drive links, tighten it a little more.

Worn-out Drive Sprocket

The chainsaw drive sprocket pushes the chain and is what generates the cutting power of the chainsaw blade. Over time the drive links in the sprocket that hold the chain in place wear down and let the chainsaw chains slip. As this happens, more and more, the internal sprocket can loosen, and the chainsaw chains will come off.

Increased Operating Temperatures

As chainsaw blades heat up and cool down, the metal will expand and contract. Operating a chainsaw that has been stored in the cold can cause fluctuations in chainsaw tension and call for mild adjustments. After running the chains in chainsaws for a few minutes, add oil and check that the tightness is still correct.

Damage to the Chain and Guide Bar

Power tools eventually wear down, and when they do, they will need to be replaced. It is important to keep an eye on when a replacement chainsaw chain is needed by checking for broken teeth and damage to the guide bar. The chainsaw guide bar shouldn’t let the chain slip or rub incorrectly against any of the rails.

Worn-Out Bar Heel

Chainsaw bar heels are the grooves in chainsaw bars that the chain rests in. As a chain pushes against wood, it is driven back against the heels, and over time, it works the grooves wider. The increased gaps affect chain tension, and replacement of the bar may be needed, so check bar heels for wear and tear.

Faulty Tensioning Mechanisms

One of the most basic components of the chain tightening system is the tension screws. Turing the screw one way tightens while the other way loosens. Over time the threads and other internal components can decay and cause the chain to slip. Check these simple fixes before looking further into other mechanical issues.

Over Tightening

This is a common novice woodworker mistake where they are unaware that some give is needed on a chain. They will over-tighten the chainsaw chain, which can lead to damaged rails and put extra stress on the chain sprocket. Make sure to give your chain some give to work as a preventative measure from over-tightening issues.

Lodged Debris

It is common for debris and jammed material to knock a chain loose on the bar during operation. If the chainsaw chain comes loose from the debris, stop the blade and clear the jammed materials carefully. Make sure the oil you are using for lubrication isn’t causing wood material to stick to the chainsaw guiding blade.

Incorrect Lubricant

The wrong lubricant can make for a dirty chainsaw chain that picks up debris and chunks of wood. Use a thin and less tacky lubricant when temperatures are low. Use thicker chainsaw lubricant in high temperatures or when the additional application of chainsaw lubricant is needed. Make sure the chain oiler is operating correctly to coat the entire chainsaw blade.

Anatomy of a Chainsaw Blade

Chainsaw Blade

There are many moving parts on a chainsaw, and it is important to know what they are to practice proper chainsaw maintenance. For the best chainsaw performance, make sure all of these parts are clean, assembled correctly, and free of any damage or defects that could endanger chainsaw users.

ChainRuns on the chainsaw bar and holds cutting teeth against woodKeep the chain at the right tension, well-oiled, and sharp
Drive SprocketPower drive that spins the chainReplace when the chain can no longer stay on drive links
Guide BarSteel bar that holds the chain and reinforces the cutting capabilities of the bladeCheck heels and rails for damage and oversized grooves
Bar HeelsRuts that house where the chain rests as it spins and cuts into the woodKeep the chain tension loose, so the chain isn’t continuously grinding against the bar
Bar RailsHold the chain in place and prevents it from moving off the bar via the sidesKeep the chain well lubricated to prevent friction and gaps large enough for a chain slip
Side PanelCovers where the chainsaw bars meet the essential component of the drive sprocket clutch and brakeMake sure it is always tightly secured to prevent dirt and debris from getting inside and gumming up the works
Tension ScrewsThe screws that hold the chain in place can be loosened or tightened to give or remove slackCheck that the threads are well-defined and not stripped whenever you tighten the chain

How To Fix a Chain that Keeps Coming Off?

If your chain keeps coming off, you will need to do more than just routine maintenance. Having to stop repeatedly while working is frustrating, and even with protective gear, loose blades can present an injury risk. If, no matter how much you tweak the screws, you can’t get your chain right, try these steps below.

1) Check the Chain Length

Chainsaw chains are not universal, and there are many different sizes for the various chainsaw models on the market. You may have gotten a chain that is just a few links too big and is slipping because it is the wrong chain for your bar. You can either buy the correct chain size or use the master link attached to every commercial chain to remove a link or two.

2) Loosen the Chain

Letting the chain out a bit, shaking it free, and clearing up any jams or debris can help everything fall back into place tighter later. While you loosen all the parts around the chain, check that nothing is damaged and everything is lubricated and intact. Run the chain along the bar until everything lines up correctly before moving on.

3) Retighten the Tension Screw

The screws that hold the drive sprocket and place the chain in the drive links can be tightened until there is just the right amount of slack on the chain. The easier way to check is with the dime method. You should be able to slip a dime between the chain and the bar easily if you have the correct tension on the chain.

4) Secure Nuts and Guiding Bar Tightly

Stihl 7010-871-0389 Chain Saw Scrench - 3 in 1 Multi Tool Wrench

Using your scrench, chainsaw screw wrench, reattach the nuts that lock the chain cover and guide bar together tightly. Hold the blade upright by the chainsaw nose and make sure the chain links are tight before screwing everything together again. Check the outer edges of the bar to make sure the blades line up the right way to cut into the wood safely.