To file a chainsaw chain, first secure the bar in a vise and ensure the chain is tensioned. Identify the correct file size for your chain’s pitch (commonly 5/32 or 3/16 inch) and match the file to the cutter’s angle, usually 30 degrees for the top plate and 10 degrees for the side plate. Place the file in the cutter’s gullet, keeping it level and at the correct angle, and push it forward in smooth strokes, filing each cutter the same number of times to keep them even. After filing, check and lower the depth gauges with a flat file so they sit about 0.025 inches below the cutter tops. Always file from the inside out and never use a back-and-forth motion.
What You Need to File a Chainsaw Chain
Before you begin, gather the correct tools. The most important is the round file, sized to match your chain’s pitch. Common sizes are 5/32 inch for smaller chains and 3/16 inch for larger ones. Using the wrong file size will not sharpen the cutter correctly and can damage the chain. Check the chain’s pitch, which is usually stamped on the drive links or listed in the manual, to determine the right file diameter.
A file guide is highly recommended, especially for beginners. It holds the file at the correct angle and depth, ensuring consistent results across all cutters. While it is possible to file freehand, a guide reduces the risk of uneven sharpening. You will also need a flat file for lowering the depth gauges and a depth gauge tool to measure the correct clearance. A small brush for cleaning debris from the chain and a vise to hold the bar steady are also useful.
Finally, have a pair of gloves to protect your hands and safety glasses to shield your eyes from metal filings. Filing produces fine metal shavings that can be sharp, so proper protection is important. With the right tools assembled, you can proceed to prepare the saw.
How to Prepare the Chainsaw for Filing
Proper preparation is essential for a good filing job. Start by securing the chainsaw bar in a vise. Clamp the bar near the base, not the tip, so the chain remains accessible. Make sure the saw is stable and will not move while you work. If you do not have a vise, you can place the saw on a sturdy workbench and hold the bar steady with your non-dominant hand, though a vise is safer and more effective.
Next, tension the chain. A loose chain will move while you file, making it difficult to get consistent strokes. Tighten the chain so it fits snugly against the bar but still allows you to pull it around by hand. Most saws have a tensioning screw on the side of the bar; turn it until the chain is firm, then retighten the bar nuts.
Before filing, clean the chain. Grass, dirt, and sawdust can clog the gullets and interfere with the file. Use a small brush or a pick to remove debris from between the cutters and drive links. A clean chain files more smoothly and gives you a better view of each cutter. Once the chain is clean and tensioned, you are ready to sharpen.
How to File Each Cutter Tooth Correctly
Filing each cutter correctly is the core of the sharpening process. Begin by identifying the first cutter on one side of the chain. Place the round file in the gullet, which is the curved area between the cutter tooth and the depth gauge. The file should sit level, parallel to the bar, and at the correct angle. For most chains, the top plate angle is 30 degrees, and the side plate angle is 10 degrees. A file guide will help you maintain these angles consistently.
Push the file forward in smooth, firm strokes, moving from the inside of the cutter toward the outside. Use only forward strokes; never file back and forth, as this dulls the file and produces an uneven edge. Apply even pressure and keep the file level throughout each stroke. After a few strokes, check the cutter to see if the metal is shiny and the edge is sharp. Do not over-file, as this removes too much metal and shortens the chain’s life.
Count the number of strokes you use on the first cutter and repeat the same number on every cutter on that side. This ensures all cutters are filed evenly. Once you finish one side, rotate the chain or flip the saw to access the cutters on the opposite side. Alternate between sides as you work to keep the chain balanced. Filing one side more than the other can cause the chain to cut crooked.
How to Check and Adjust the Depth Gauges
The depth gauges, also called rakers, control how deeply each cutter bites into the wood. If they are too high, the chain will not cut effectively; if they are too low, the chain may grab and cause kickback. The correct clearance is about 0.025 inches below the top of the cutter, though this can vary by chain model. Check your manual for the exact specification.
To measure the depth gauge, use a depth gauge tool. Place the tool over the cutter so it rests on the top of the cutter and the depth gauge. The tool has a slot that shows how much of the gauge protrudes above the cutter top. If the gauge is too high, file it down with a flat file. Hold the flat file level and file the top of the gauge in smooth strokes, checking frequently to avoid removing too much metal.
After filing the depth gauges, use the tool again to verify the clearance is correct. Repeat the process for every depth gauge on the chain. Consistent depth gauge height is just as important as even cutter filing. If the gauges are uneven, the chain will cut unevenly and may vibrate excessively. Take your time with this step to ensure a smooth, safe cutting experience.
How to Keep All Cutters Even
Keeping all cutters even is crucial for a straight, efficient cut. The simplest method is to count strokes. Use the same number of strokes on every cutter, with the same pressure and angle. This gives each cutter the same amount of material removal. If a cutter is noticeably duller than others, you may need a few extra strokes, but try to stay consistent overall.
Alternate sides as you file. Work on one side of the chain, then move to the other side. This prevents one side from becoming sharper than the other, which can cause the chain to pull to one side during cutting. After filing, inspect all cutters visually. They should look uniform in shape and shine. If any cutter looks different, re-file it to match the others.
Finally, test the chain by running it on the saw. A properly filed chain should cut smoothly and produce consistent sawdust. If the cut is rough or the saw pulls to one side, check for uneven cutters or depth gauges. With practice, you will develop a feel for the correct stroke count and pressure, making the process faster and more reliable.
Common Filing Mistakes and How to Avoid Them
One of the most common mistakes is filing at the wrong angle. If the top plate angle is too steep or too shallow, the cutter will not bite properly, and the chain may cut slowly or vibrate. Always use a file guide or check the angle against the markings on the cutter. Filing freehand without a guide increases the risk of angle errors, especially for beginners.
Uneven strokes are another frequent problem. If you apply more pressure or use more strokes on some cutters than others, the chain will be unbalanced. This can cause the saw to cut crooked or bind in the wood. Count your strokes and maintain consistent pressure to keep all cutters even.
Filing in the wrong direction is also a common error. Always file from the inside of the cutter toward the outside, using forward strokes only. Filing backward or using a back-and-forth motion dulls the file and creates a rough edge. If you notice the file slipping or the edge looking ragged, check your technique and adjust.
Finally, do not neglect the depth gauges. Filing the cutters without adjusting the depth gauges can leave the chain cutting poorly, even if the cutters are sharp. Always check and lower the depth gauges after filing to maintain proper clearance. By avoiding these mistakes, you will keep your chain sharp and your saw cutting smoothly.
