How to Sharpen a Chainsaw Chain on a Small Farm

Your chainsaw is throwing fine dust instead of chips, pulling to one side and making you lean on it to get through a fence post. That is a dull chain, and on a small farm it costs you fuel, bar wear and a sore back every time you clear a fallen limb. Learning to sharpen a chainsaw chain yourself takes about 20 minutes per sharpening once you have done it a few times, and the tools cost less than two professional sharpenings.

This is the method I use on our 18 inch farm saw and a smaller 14 inch saw we keep for fence lines. It works on any standard round-ground chain.

What you need to sharpen a chainsaw chain

• A round file in the right diameter. Most 3/8 inch low profile chains take a 5/32 inch file. Standard 3/8 and .325 pitch chains usually take 3/16 inch. Full 3/8 chains on bigger saws take 7/32 inch. The size is often stamped on the drive link or listed in the saw manual.
• A file guide. A simple guide that clips over the file and shows 25 and 30 degree lines costs about $10 to $15. It is the difference between a chain that cuts straight and one that wanders.
• A flat file and a depth gauge tool. Around $8 to $12 for the pair.
• A bench vise or a stump vise. A stump vise you tap into a log costs $20 and lets you sharpen in the field.
• Gloves, a rag and a paint marker.

Total outlay is roughly $45 to $60. A shop sharpening runs $12 to $18 per chain in most rural areas, plus the drive.

How to tell when the chain needs work

A sharp chain pulls itself into the wood with only the weight of the saw. It throws thick, square chips. A dull one throws powder, smokes on hardwood and needs pushing. Other signs:

• The saw drifts to one side in a straight cut, which usually means the cutters on one side are longer or sharper than the other.
• You hit dirt, a fence staple or a rock. Even one second in soil can dull every cutter.
• You have run two full tanks of fuel since the last touch-up.

Step by step: sharpen a chainsaw chain with a file

1. Shut the saw off and secure it. Clamp the bar in the vise so the chain sits about 2 inches above the jaws. Engage the chain brake, then release it each time you need to advance the chain.
2. Tighten the chain slightly. A little extra tension stops the cutter from rocking under the file. Loosen it back to normal before you run the saw.
3. Find the shortest cutter. Look along the top plates. Mark the shortest cutter with a paint marker. Every other cutter gets filed back to match it, otherwise the saw will pull.
4. Set the angle. Hold the file guide flat on the cutter with the 30 degree line parallel to the bar, unless your chain maker specifies 25 degrees. Keep the file level, not tilted up or down.
5. File from inside to outside. Push the file from the inner face of the cutter toward the outer edge. File on the push stroke only, and lift on the return. Three to five smooth strokes per cutter is normal for a touch-up.
6. Do one side first. File every second cutter on one side, all the way around, starting from your marked cutter. Then flip around to the other side of the saw and repeat for the opposite cutters.
7. Count strokes. Give every cutter the same number of strokes. If the marked cutter took four, they all get four.
8. Check the depth gauges. After every third or fourth sharpening, lay the depth gauge tool across the chain and file any raker that sticks up through the gauge opening with the flat file. Round the front edge slightly afterward.

Run the saw for a test cut in a piece of firewood. You should see chips within the first inch.

Common mistakes that ruin a chain

Holding the file too high or too low

About one fifth of the file's diameter should sit above the top plate. Too high and you create a blunt hook that bounces. Too low and you cut into the gullet and weaken the cutter. The guide solves most of this.

Uneven cutters

If one side is consistently longer, the saw curves in every cut. When I see a crooked cut on our saw, I measure cutters with calipers and file the long side back. It takes ten extra minutes and saves the bar.

Ignoring the bar

A sharp chain on a worn bar still cuts crooked. Flip the bar every time you change chains, clean the groove with a putty knife and file off any burr on the rails. Keeping a short record in a maintenance log that actually gets used makes it easy to see when the bar was last flipped.

Why I do not recommend an electric grinder for most small farms

A lot of advice says to buy a bench chain grinder and save time. For a commercial cutter going through ten chains a week, that makes sense. For a small farm running one or two saws, I disagree. A $90 grinder removes metal fast and heats the cutter edge if you hold it too long, which softens the steel and dulls it again within a tank. Cheap grinders also drift out of adjustment and give you mismatched cutters without you noticing.

Hand filing in the field after every tank or two keeps the chain close to sharp, so you are only taking off a few thousandths of an inch each time. A chain cared for this way can last 10 to 15 sharpenings longer than one that gets ground back from fully dull. Keep the grinder idea for later, if you start selling firewood by the cord.

How often to sharpen and when to replace

Touch up the chain every time you refuel during heavy cutting, or immediately after you hit dirt or metal. Replace the chain when the top plate of the cutters is worn back to about 1/8 inch, when a cutter is cracked, or when the chain has stretched so far that the adjuster is at its limit. A new 18 inch chain costs $25 to $40, which is cheap insurance compared with a new bar and sprocket.

Keep a spare sharpened chain in the truck. When one dulls in the middle of a job, swap it and sharpen the old one in the evening. That habit fits well with the advice in buying secondhand machinery as a calculated risk: maintenance is what makes older tools pay.

Frequently asked questions

How many times can you sharpen a chainsaw chain?

A good chain handled with light hand filing can be sharpened 10 to 15 times or more. The limit comes when the cutters wear back to about 1/8 inch of top plate. Hitting rocks or grinding aggressively shortens that life a lot.

What size file do I need for my chainsaw chain?

Most homeowner and farm saws with 3/8 inch low profile chain use a 5/32 inch file. Standard 3/8 and .325 chains usually use 3/16 inch. Check the stamp on the drive links or the saw manual to be sure.

Why does my chainsaw cut crooked after sharpening?

Crooked cuts almost always mean the cutters on one side are longer or filed at a different angle than the other side. A worn or burred bar can cause it too. Measure the cutters, file the long side back to match and dress the bar rails.