A chainsaw should pass through a log like a train on straight rails. When the cut bends left or right, the guide bar may become trapped before it reaches the bottom. The saw may also leave a curved face that makes firewood rounds wobble on the splitter.
Uneven cutter teeth are the most common cause of a chainsaw not cutting straight. Teeth on one side may be shorter, duller, or filed at a different angle. A worn guide bar can cause the same fault. Begin with the chain, then inspect the bar rails, chain tension, drive sprocket, and oil flow.
High-End Shop Picks Over $2,000 as a Set
You do not need a full repair shop to correct a crooked cut. A round file, filing holder, raker gauge, flat file, and bar cleaner may be enough. The equipment below suits a large firewood room or saw-service business. Bought as a set, the total can pass $2,000.
| Equipment | Best Use | Amazon Link |
|---|---|---|
| Oregon 620-120 Chain Grinder | Matching cutter length and filing angles across many chains | Compare Oregon 620-120 grinders |
| Yost ADI-5 Bench Vise | Holding a guide bar steady during hand filing | Compare Yost ADI-5 vises |
| Seville Classics UltraHD Workbench | Creating a firm saw-care station | Compare UltraHD workbenches |
| Fluke 87V MAX Multimeter | Checking electric saw switches, cords, and motor circuits | Compare Fluke 87V MAX meters |
| FLIR Thermal Camera | Finding hot bar rails, bearings, motors, and clutch parts | Compare FLIR thermal cameras |
| Chain Breaker and Rivet Spinner | Repairing and building chain loops | Compare chain repair sets |
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Quick Diagnosis Table
| What the Saw Does | Probable Cause | First Check |
|---|---|---|
| Pulls left during every cut | Right-facing cutters are sharper or longer | Compare both rows of cutters |
| Pulls right during every cut | Left-facing cutters are sharper or longer | Compare both rows of cutters |
| Starts straight, then bends | Worn bar rails or a bent guide bar | Remove and inspect the bar |
| Cut becomes worse after hand filing | Unequal file strokes or wrong filing angle | Measure cutter lengths |
| Chain leans inside the bar groove | Worn rails or the wrong chain gauge | Check chain and bar markings |
| Saw chatters and grabs | Rakers are uneven or too low | Check each raker with the matching gauge |
| Bar smokes during a crooked cut | Poor oil flow, dull cutters, or excess tension | Stop and inspect lubrication |
Stop Forcing a Crooked Cut
A sharp, well-set chain should pull itself into wood with light hand pressure. Do not twist the rear handle to force the guide bar back toward the cutting line. Side pressure can widen the bar groove and wear one rail faster than the other.
Shut the saw off when the cut begins to curve. Remove the battery from a cordless model. Unplug a corded model. Let a gas saw cool, then remove the spark-plug cap before taking off the side cover.
Wear thick gloves during every chain check. Cutter teeth can open skin even when the saw has no power.
Uneven Cutter Length Is the Main Cause
A chainsaw chain has two rows of cutters. One row faces left, while the next faces right. Both rows must take nearly equal bites from the wood.
Suppose the right-facing cutters are longer and sharper. They remove more material from their side of the kerf. The chain then pulls toward that side. The guide bar follows, and a straight cut becomes a curve.
This fault often begins after one side of the chain strikes soil, stone, wire, or dirty bark. The damaged teeth need more file strokes than the teeth on the opposite side. A rushed filing job may leave them shorter or duller.
Find the shortest cutter on the chain and mark it with a paint pen. Measure it from the rear edge to the front cutting corner. Compare it with cutters from both rows.
File the longer cutters until they come close to the marked tooth. Do not remove extra metal from the shortest tooth merely to give every cutter the same number of strokes.
One Side of the Chain May Be Duller
Cutter length can match while sharpness does not. A shiny line along the top cutting edge means that the edge is still blunt. The line must disappear before the cutter can bite cleanly.
Operators often file one row better because of hand position. A right-handed person may hold a good angle on one side and a poor angle on the other. The weak row skates across the wood while the sharper row pulls the saw sideways.
Clamp only the flat guide bar in a vise. Use rubber, aluminum, or wooden jaw covers so bare steel jaws do not mark the bar.
File from the inside of each cutter toward the outside. Push the file through the tooth in one direction. Lift it away before the return stroke.
Turn the saw or move your body when you switch cutter rows. Do not twist your wrist into an awkward position. A firm stance makes it easier to keep the file level.
Check the Filing Angle
Each cutter must follow the angle stated for that chain. Many chains place a witness line on the top plate. The line gives a visual target for the file.
One row filed at a steep angle may cut more aggressively than the opposite row. A row filed too flat may take a weak bite. The mismatch can steer the saw through the log.
Use a filing holder that matches the chain pitch. Keep the holder level with the guide bar. The marked angle line should remain parallel with the bar or chain centerline, based on the holder design.
Do not guess the file diameter. A file that is too large may leave a blunt upper edge. A file that is too small can create a hooked cutter that grabs and wears quickly.
Check the Rakers
The small raised part ahead of each cutter is called a raker. It controls how much wood the cutter removes with each pass.
Unequal rakers can steer the chain. A low raker lets its cutter take a larger bite. A high raker lets its cutter skim across the wood. When one row has lower rakers, that side can pull harder.
Place the correct raker gauge over the chain. File only the metal that rises above the gauge slot. Round the leading edge by the method given for the chain.
Do not lower rakers by sight alone. Rakers set too low can make the chain chatter, grab, and react with greater force at the bar nose.
Inspect the Guide Bar Rails
The guide bar has two narrow rails that hold the chain upright. The chain cannot travel straight when one rail is lower than the other.
Most wear appears on the lower section of the bar because that area does much of the cutting. Operators who rarely turn the bar over may wear one face much faster.
Remove the bar and clean it. Stand it upright on a flat bench. Look across both rails from the end. They should be close to equal height.
Place a small square against the rails when you have one. A chain that leans to one side points toward low or flared rail edges.
Minor rail burrs can be removed with a flat bar file. Keep the file square to the side of the bar. A rail that has lost a large amount of metal calls for bar replacement.
Check for a Bent Guide Bar
A bent guide bar acts like a curved railway track. Even a perfectly filed chain will follow its path.
Lay the cleaned bar on a known flat surface. Press gently near each end and watch for rocking. Turn it over and repeat the check.
Look down the bar from the mounting end toward the nose. Replace it when you see a bend, twist, crack, or crushed groove.
Do not try to straighten a badly bent bar with a hammer or vise. The rails may crack, and the bar can bend again during use.
Check the Bar Groove
The chain drive links travel inside the guide-bar groove. Heavy wear can make this groove too wide. The chain then leans from side to side under cutting pressure.
Clean the groove with a plastic bar cleaner or thin wooden scraper. Clear the oil holes near the mounting end.
Fit a clean section of chain into the groove. Push gently against the side of a cutter. A small amount of movement is normal, but the chain should not lean far enough to place the cutter against the bar body.
Replace the guide bar when the groove no longer holds the chain upright. A fresh chain will not correct an oversized groove.
Confirm the Chain Gauge
The chain gauge is the thickness of the drive links. It must match the groove width stamped on the guide bar.
A chain that is too narrow may lean inside the groove. A chain that is too thick may bind, heat the bar, or refuse to move freely.
Check the markings on the bar and chain package. Common gauge sizes include .043, .050, .058, and .063 inch. Do not rely on bar length alone.
Pitch and drive-link count must also match the bar and drive sprocket. A chain with the wrong fit can move poorly and wear the cutting set at a rapid rate.
Set the Chain Tension Correctly
A very loose chain can lean and wander through a cut. A chain pulled too tight creates heat and heavy drag.
Loosen the bar nuts slightly. Hold the guide-bar nose upward. Turn the tension screw until the drive links remain inside the groove and the chain rests against the lower rail.
Pull the chain around the bar by hand while wearing gloves. It should move with steady resistance. Tighten the bar nuts while the nose remains raised.
Check the tension again after tightening. A new chain may loosen during its first work sessions, so stop and inspect it often.
Inspect the Drive Sprocket
The drive sprocket pulls the chain around the guide bar. Deep grooves in the sprocket can hold the drive links at an angle or make chain movement uneven.
Remove the clutch cover after disconnecting all power. Check the sprocket teeth for grooves, chips, cracks, blue heat marks, or side wobble.
Some saws use a replaceable rim sprocket. Others use a spur sprocket built into the clutch drum. Fit the exact part listed for the saw.
A new chain placed on a badly worn sprocket may develop poor tracking and early wear. Replace the worn sprocket before fitting an expensive new chain and bar.
Check Bar-Oil Flow
Poor lubrication can wear one rail faster than the other. A dry chain can also heat, stretch, and bind during a long cut.
Fill the oil reservoir with bar-and-chain oil. Clean the oil outlet on the saw and both oil holes in the guide bar.
Refit the cutting set and run the saw briefly with the bar pointed toward pale cardboard. A light line of oil should appear.
Stop the saw when no oil reaches the cardboard. A blocked passage, damaged hose, failed pump, or worn pump drive may need shop work.
Keep the Chain Away From Soil
Soil contains sand and stone. One quick touch can dull several cutters on the lower side of the chain. The saw may begin pulling sideways on the very next cut.
Raise logs with a cant hook, timberjack, log stand, or scrap wood. Stop the cut before the chain reaches the ground. Roll the log and finish from the other side.
Brush mud and grit from the bark when possible. Watch for nails, fence wire, gravel, and concrete hidden inside old yard trees.
Do Not Blame Your Arms Too Quickly
Operator position can affect the first inch of a cut, but a saw that bends the same way through every log usually has a chain or bar fault.
Stand with both feet firm. Hold the front handle with your left hand and the rear handle with your right hand. Keep your thumbs wrapped around both handles.
Begin with the chain at full speed. Let the bumper spikes rest against the bark when the saw has them. Do not push sideways on the rear handle.
Test the repaired saw on a stable log with a flat end. Make one light cut without trying to steer it. A healthy cutting set should pass through on its own line.
When to Replace the Chain
Replace the chain when several cutters have major damage, cracked metal, loose rivets, bent drive links, or teeth filed back to their wear marks.
A chain with a large difference between the shortest cutter and the remaining teeth may take too much time to correct by hand. A bench grinder can match the teeth, but every cutter loses metal during the correction.
Keep a spare chain ready. A clean replacement loop offers a quick test. When the saw cuts straight with the spare chain, the old chain caused the fault.
When to Replace the Guide Bar
Replace the bar when it is bent, cracked, twisted, or badly worn. The same applies when the groove has become too wide or the rails cannot be filed square again.
A seized nose sprocket also calls for replacement on bars with a fixed nose. Some large solid bars have replaceable tips, but that repair needs matching parts and correct rivet work.
Fit a bar with the right mount, pitch, gauge, and approved length for the saw. Move the chain by hand before restoring power.
Frequently Asked Questions
Why does my chainsaw always cut to the left?
The cutters that face right may be longer or sharper than the cutters that face left. Uneven guide-bar rails can also pull the saw left.
Why does my chainsaw always cut to the right?
The left-facing cutters may be doing more work. Compare tooth length, sharpness, filing angle, and raker height on both rows.
Can a dull chain make a crooked cut?
Yes. The cut may bend when one row of cutters is duller than the other. A chain that is equally dull on both sides usually cuts slowly rather than sharply to one side.
Can a guide bar make a chainsaw cut sideways?
Yes. Uneven rails, a wide groove, a bend, or a twist can steer the chain away from a straight line.
Can the wrong chain cause a curved cut?
Yes. A chain with drive links that are too narrow for the bar groove can lean under pressure. The pitch, gauge, and drive-link count must match the cutting set.
Should every cutter be exactly the same length?
Small differences may not be easy to feel, but large differences between rows can steer the saw. Match the cutters as closely as practical without filing past their wear marks.
Why did my saw start cutting crooked after sharpening?
One row may have received more file strokes, a different angle, or more pressure. The rakers may also differ from one side to the other.
Best Fix Order
Stop the saw and remove its power. Compare the cutters on both rows. Look for different lengths, shiny blunt edges, and mismatched filing angles.
Mark the shortest cutter. File the remaining cutters to a close match. Check every raker with the correct gauge.
Clean the guide-bar groove and oil holes. Inspect the rails for unequal height, burrs, a wide groove, a bend, or a twist.
Confirm that the chain gauge, pitch, and drive-link count match the bar and sprocket. Set the tension, check the drive sprocket, and test the oil flow.
Fit a known-good chain when the cause remains uncertain. Replace the guide bar when the new chain still leans or cuts in a curve. A straight cut needs two equal rows of sharp teeth and a guide bar that holds them like rails beneath a train.