How to sharpen a chainsaw

You will need - a round file and guide; and a flat file and guide to keep your chain sharp.

Round files and guides vary in size depending on the saw chain. As a rule of thumb, most saw chains use the following file sizes.

1/4p chain3.2mm file
3/8p & 1/4 chain4.0mm (5/32) file
.3254.8mm (3/16) file
3/8 & .4045.5mm (7/32) file

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Introduction - Keeping your chainsaw sharp is important, a sharp chain decreases the stress caused to both your chain and saw, prolonging the life of each component and reducing the overall running costs.

A blunt chain will over heat. This causes it to stretch which in turn wears both the guide bar and drive sprocket. In addition, the added resistance requires more power making the engine work harder than it needs to, causing more wear internally and using more fuel.

You will know when your chainsaw chain is blunt because it will start to produce dust rather than wood chips. You should sharpen your saw chain before it reaches this point. A good place to start would be to sharpen the chain every time you fill up with fuel. It's easier and more efficient to sharpen little and often rather than waiting a long time.

The following guide will show you through the various steps that are advised for sharpening your chainsaw chain.

Filing the Chain - The chainsaw and guide bar should be in a fixed position to ensure good stability, and in order for you to have both hands free for filing. It is easiest if you use something like a filing vice (pictured right) to secure the guide bar. Secure the chain by activating the chain brake.

The cutting teeth on the chain must be filed according to three different angles: filing angle, side plate angle and top plate cutting angle. The angles vary depending on the type of chain you have. If you use a filing gauge you do not need to think about the different angles to ensure a good result. Just follow the instructions and you will get the right angles on the cutting tooth.

    Bar mounted file guides are also available to achieve the perfect angle.
  • 1. Start with the cutting teeth. Use the round file and filing guide that is designed for the type of chain that you have (see table at top of page).
  • 2. Find the cutting tooth that has the most damage and place your file and guide over that tooth to start.
  • 3. File the cutting tooth away from you with smooth strokes. The filing angle is then 25-35° depending on the type of chain. File the tooth back beyond the damaged area, the cutting edge should be straight, clean and sharp.
  • 4. Proceed to file every other cutting tooth on that side of the chain. It is important to file every tooth so that it is the same length, unless you're sculpting bananas!
    * Tip - Some people find it easiest to count the number of strokes required so that they can replicate the same action for each cutting tooth, if you do then it is important to apply a constant and equal amount of pressure for each stroke. Position yourself at a comfortable angle to the saw and maintain it throughout the sharpening process to help achieve this.
  • 5. Once you have finished filing all the cutting teeth on one side, loosen the vice and then attach the guide bar from the other direction.
  • 6. Then sharpen the cutting teeth in the same way from the opposite direction.

Freehand filing - You can also file without the filing guide but be sure to maintain the original angles for the cutting tooth. To maintain the correct angle and depth of the cutting teeth, we still recommend that you use the filing guide. Avoid filing in a way that produces a hook as the chain will be too “aggressive” as a result. This means that the saw is exposed to unnecessary strain and the user to increased vibration. The image on the left shows how a tooth should look when correctly sharpened.

Replace the chain - It is time to replace the chain when the longest portion of the cutting tooth is less than 4 mm or if you find cracks.

Depth gauge - The height difference between the position of the depth gauge and the tip of the tooth (depth gauge clearance) determines how much the cutting tooth will cut. It works much like a plane. When the plane is set up with minimal cutting blades, the plane takes a very little amount of wood. The same thing happens with the saw chain if the distance between the depth gauge clearance lip and the tip of the tooth is too small. It is also not good if the depth gauge clearance lip has been filed down too much. The cutting tooth will then cut too deeply into the wood. The cut is more aggressive with high vibrations as a result. The risk of kickback increases and the chainsaw is exposed to unnecessary stress.

Filing the depth gauge - We recommend that you file the depth gauges after you have filed the cutting teeth 3-5 times during normal wear.

  • 1. Position the depth gauge following the manufacturer's instructions, holding it firmly with one hand. Some depth gauges have different positions depending if you're cutting hard or soft wood, whereas others use a universal position.
  • 2. Take a flat file in your other hand and file the depth gauge until the file engages the gauge.
  • 3. Now continue to file all the depth gauges on the chain.