Why does my chainsaw cut crooked?

The short answer

A chainsaw cuts crooked when the two sides of the chain are not cutting equally. The saw pulls toward whichever side has the sharper, longer cutters, and the cut curves away from square. Sharpening unevenly is the most common cause. A damaged bar and a worn chain drive are the next places to look.

Start with the chain

University of Missouri Extension lists the signs that a saw needs sharpening, and the first on the list is blunt: "The saw is cutting crooked" and "the cut produces fine sawdust instead of chips" are both on it.^[3] A dull chain does not bite evenly, so the saw wanders as you push it.

Chains go dull in the yard. The extension service warns that contact with dirt, rocks or metal will quickly dull and nick the cutting teeth.^[3] If you only hit one thing, such as a buried nail on one side of a log, the damage is often on a few cutters on one side, and that alone is enough to steer the saw.

Hand-sharpening can create the problem too. If you file left-hand cutters harder than right-hand ones, or use a different angle on each side, one side ends up sharper and longer. Husqvarna notes that the filing angles vary with the type of chain, and advises freehand filers to maintain the original angles of the cutting teeth.^[1] A filing gauge takes the guesswork out of that, and the same number of strokes on every cutter keeps the lengths matched. Our guide to how to sharpen a chainsaw chain walks through it.

Then check the bar

If the chain looks even and the saw still wanders, the bar is next. The bar should be straight.^[2] To check, lay it on a flat surface and look for light underneath. A curved bar needs replacing.^[2]

Also look along both bar edges, called the rails. Check both edges for burrs and file them off.^[2] Uneven wear on the rails lets the chain lean to one side in the cut.

Wear shows up as looseness. If the chain wiggles side to side when properly tightened on the bar, the bar is due for replacement.^[2] To slow the wear, flip the bar over each time the chain is sharpened so both sides wear evenly.^[2]

Tension matters here as well. Husqvarna warns that a slack chain, like an overly tight one, can cause premature wear on the bar.^[1] If you are not sure how tight is right, see how to adjust chainsaw chain tension.

Check the drive end

The chain is pulled by the sprocket at the engine end, so a worn sprocket can make the chain run unevenly. The checklist from University of Georgia Extension includes checking the sprocket teeth for wear.^[2] If they look hooked or chewed up, a saw dealer can replace the sprocket.

A quick way to diagnose it

Make a test cut in a clean log with the saw at full throttle, letting the saw's weight do the work. Look at the sawdust. Chips of the same size from both sides suggest even cutters. If one side throws chips and the other throws dust, the chain is uneven. If the cut curves the same direction every time even after resharpening, suspect the bar.

Fix it in order

1. Rule out the chain by resharpening both sides evenly, or by fitting a new chain if the cutters are short.
2. Rule out the bar by checking that it is straight, deburring the rails and testing for side-to-side wiggle.
3. Look at the sprocket.
4. Flip the bar and make another test cut.

If you are unsure whether the chain is past saving, read should I sharpen my chainsaw chain or replace it.

Stop and call a pro if

• The bar is bent, badly worn or the chain wiggles on it. The bar needs replacing, and a small engine shop can fit the right one for your saw.
• The sprocket teeth are worn. A shop can replace the sprocket and check the clutch drum behind it.
• The cutters are nicked, cracked or very uneven. A shop can regrind the chain, or you can fit a new one. See what sharpening costs in Virginia.
• The saw still cuts crooked after a fresh chain and a good bar. There may be something else wrong with the saw that needs a shop look.

Getting help in Virginia

Browse more small engine repair answers, or find a local chain sharpening and saw repair pro. When you are ready, describe the job and local pros can quote it.