The cutting teeth on a chainsaw chain should point away from the engine on the top of the bar. If you look down at the top surface of the bar, the sharp teeth should be angled towards the tip of the bar. On the underside, they point back towards the engine. This is the only correct direction — fit it backwards and the saw simply won’t cut.
It’s a surprisingly common mistake, especially among people fitting their first replacement chain. The chain won’t damage the saw immediately if you run it backwards, but you’ll get no cutting action, the chain will heat up, and you’ll waste fuel thinking the chain has gone dull.
The Simple Rule for Chainsaw Chain Direction
On the top of the bar, the cutting edges point forward (towards the nose of the bar). On the bottom of the bar, they point backwards (towards the engine).
Think of it this way: the chain rotates clockwise when you look at the right side of the saw. The top of the bar moves towards the tip, carrying the cutting teeth forward. The bottom half moves back towards the engine, and those teeth are angled to point backwards.
Every chain link has two key features:
- The cutting tooth — a sharp corner that faces in the direction the chain moves. On top of the bar, this points towards the nose.
- The drive link (the connecting segment that sits in the sprocket groove) — has a small notch or profile that only fits one way in the bar groove. This notch points in the direction of travel.
If you try to fit the chain backwards, the drive links won’t sit properly in the groove, and the chain will rattle or jump off. Even if you force it on, the cutting teeth are pointing the wrong way and won’t bite into the wood.
How to Identify the Correct Chain Direction
Before you install the chain, lay it on a flat surface and check the direction:
- Look at the chain from above, as if you’re looking down at it sitting on a table.
- Identify one of the cutting teeth — the bit that’s actually sharp and angled.
- The cutting edge should be pointing at an angle towards one direction. That direction is the way the chain should move.
- Pull the chain gently along the table in one direction — you’ll feel it drag. Pull it the opposite way — it should glide smoothly. The smooth direction is the wrong way; the direction where it catches is the right way.
Now, when you fit the chain on the bar, the “right way” (the direction where it catches when pulled by hand) should be forwards on the top of the bar.
Another quick check: hold the bar horizontally and look at the sprocket (the toothed wheel at the nose). The chain should wrap around it so that on top, the cutting teeth are leading into the sprocket (pointing “uphill” into the curve). On the bottom, they trail away.
What Happens If You Fit the Chain Backwards?
If you fit a chainsaw chain backwards, three things happen:
- No cutting action. The teeth don’t bite into the wood; they bounce or slide off. You’ll press the saw into a log and nothing will happen.
- The chain heats up. Friction between a backwards-running chain and the bar is higher than normal. The bar gets hot, the chain stretches faster than usual, and you’ll start to smell burning chain oil after a minute or two.
- The chain stretches and loosens rapidly. Within a few minutes of running a backwards chain, it will have stretched so much that it becomes dangerously loose. It may slip on the sprocket or drop off the bar.
The good news: running a backwards chain for a few seconds won’t destroy the saw. The bad news: many people don’t realise their chain is on backwards. They think the chain has gone dull, so they sharpen it (which makes it worse). They adjust the fuel mixture thinking the engine is struggling (it’s not). They may run a backwards chain for weeks without realising, and by then the chain is stretched and damaged beyond repair.
If you suspect your chain is backwards, stop the engine immediately and check the direction before running it again.
How to Check Your Chain Direction Before Installation
Always verify direction before you tension the chain on the saw:
| Check | What to Look For | Result |
|---|---|---|
| Pull the chain by hand along the top of the bar | Does it move smoothly or catch? | Smooth = top surface is correct. Catching = you’ve installed it backwards. |
| Look at the cutting tooth angle | On the top surface, do the teeth angle towards the nose? | Yes = correct. Flat or pointing back = backwards. |
| Check the drive link profile | The drive links should sit evenly in the bar groove | Even fit = correct. Rocking or loose = check direction. |
| Spin the sprocket by hand | Does the chain rotate smoothly in one direction only? | Yes = correct. Rough or jamming = backwards. |
How to Fit a Chainsaw Chain in the Correct Direction
Step-by-step installation:
- Stop the engine and let it cool completely.
- Remove the clutch cover (side cover) by loosening the nuts or bolts holding it.
- Loosen the bar mounting bolts slightly — the bar should move forward/back freely.
- Remove the old chain and bar if you’re replacing both.
- Fit the new bar, ensuring the oil port on the bar aligns with the oil pump outlet on the engine housing.
- Take the new chain and lay it on a table. Double-check the cutting tooth direction — teeth should point in one direction. That’s the “forward” direction.
- Start threading the chain around the sprocket at the nose. The top surface of the chain should move towards the tip of the bar as you wrap it around. The cutting teeth on top should point towards the nose.
- Continue wrapping the chain down the bottom of the bar and back around the main sprocket (at the engine end).
- Check: pull the chain gently along the top surface. It should catch/resist, not glide smoothly. If it glides, you’ve fitted it backwards — remove and flip it.
- Tighten the bar mounting bolts until snug (not over-tight).
- Adjust chain tension: lift the chain at the nose — it should pull away from the bar by about 3–5mm, then snap back when released. Adjust the tensioner screw until this is right.
- Check again: the chain should not sag below the bar, and it should move freely by hand.
Does Chain Direction Matter for Different Saw Types?
Petrol saws: Yes, direction matters absolutely. Fit it backwards and it won’t cut.
Electric saws: Same rules apply. Makita, DeWalt, and Milwaukee battery saws all require the same direction — teeth forward on top, back on bottom.
Pole saws: Same again. The direction rule is universal across all chainsaw types.
Milling attachment chainsaws: Same direction rule, though milling chains have a different link design. The principle is identical.
Top Tips for Getting Chain Direction Right
- Always check direction on a new chain before you fit it on the saw. Lay it flat and trace the tooth angle with your finger.
- Take a photo of your old chain (top surface) before you remove it. Use that as a reference for your new chain.
- If you’re ever uncertain, install the chain, spin the sprocket by hand, and feel which direction it rotates smoothly. If it catches and locks up, the chain is backwards.
- After fitting a new chain, run the saw for 10 seconds without cutting (let it warm up). You should hear the chain cutting air smoothly, not grinding. If it sounds wrong, stop and check direction.
- Mark your bar with a small piece of tape on the top surface. Use that tape to remind yourself which way is “forward” when you fit your next chain.
Watch: Video Guide
Frequently Asked Questions
What if I run my chainsaw with the chain on backwards?
The saw won’t cut. You’ll feel vibration and hear a grinding sound. The bar and chain will heat up rapidly due to friction. Stop the engine immediately and check the direction.
Can a backwards chain damage my saw?
Not immediately. However, a backwards chain stretches rapidly due to overheating, and it will eventually drop off or snap. Running a backwards chain for extended periods can damage the sprockets.
How do I remember which way is correct?
On the top of the bar, teeth point forward (towards the nose). Pull the chain along the top by hand — if it catches and resists, that’s the correct direction for the top surface.
Do electric chainsaws have the same chain direction rule?
Yes, absolutely. Battery saws like Makita and DeWalt use the same direction convention. Teeth forward on top, back on bottom.
Can I fit the chain either way if I adjust the tension?
No. Tension adjustment doesn’t change the cutting direction. A backwards chain won’t cut no matter how tight you make it.
What if the chain seems to fit both ways?
It shouldn’t. If the chain fits equally well in both directions, you may have an older chain with symmetrical links, or the bar groove is damaged. Check the cutting tooth angle — one side is definitely sharper/more angled than the other. That side goes forward on top.
How often should I check my chain direction?
Every time you fit a new chain. After that, the direction is fixed on the bar (the bar groove and sprockets are designed for one direction only), so you won’t accidentally reverse it.
Ready to Install Your Chain?
Remember: teeth forward on the top of the bar. When in doubt, test the chain direction by hand before you tighten it on the saw. For help finding the correct replacement chain for your saw, see our chainsaw chain compatibility guide.
Need a new chain? Find replacement chains on Amazon UK.
