How To Sharpen A Chainsaw Chain

A blunt chainsaw chain is not only inefficient - it can be dangerous. Guidance from the Health and Safety Executive explains that maintenance is a big part of chainsaw safety and will help to prevent some of the chainsaw injuries that are reported in the arborist and forestry industry every year.

You’ll know that your chainsaw needs sharpening when you have to apply more force at the bar to cut. The chainsaw will be floating on the cut instead of slicing into it. Another sign is that the chain is spitting out dust instead of chips of wood. This means that it is staying in one position for too long instead of moving down through the wood.

A dull chain is more likely to kick back and catch in wood which will propel the bar upwards. In addition, it is dangerous to apply excessive pressure onto the bar because it makes it more likely to slip and cause an accident.

Here then, is our step-by-step guide on how to sharpen a chainsaw.

1. Gather the correct equipment

The most important piece of equipment is a chainsaw file that is the correct size for the teeth on your saw’s chain. Chainsaws have teeth of different sizes so you will need to check the manual to find the correct one for your saw. You could also use the chain identification number which you will often find stamped on the drive link, or for many Stihl or Husqvarna saws you can use our chainsaw chain wizard to identify the correct chain and check the description to find the matching file size.

The most common sizes are 5/32” (4.0mm), 3/16” (4.8mm) and 7/32” (5.5mm). You can buy Stihl chainsaw files in packs of 3, whilst Oregon Chainsaw Files come as a box of 12.

You will also need a file guide which will hold the file at a uniform depth when you are sharpening each cutter. The Stihl Roller Filing Guide includes a file guide which can be used for precise filing. It also has an integrated file tip which you can use for adjusting the setting of the depth gauge after sharpening. It comes in 3 sizes (4.0mm, 4.8mm and 5.5mm) and comes with an instructional DVD.

You will also need a flat file and a depth gauge for resetting.

2. Check the chain thoroughly

First, do a quick health check of the chain - if you find teeth which are significantly chipped or bent or have bits broken off them, you should replace the chain rather than sharpen it, as the chain could be unsafe to use. 

On most chains, there is a mark on the top of the tooth showing the minimum usable size of the tooth. If the links have already been sharpened back to this, or close to this, then the chain should be replaced rather than sharpened.

3. Clamp the chainsaw and find the lead cutter

Before you start filing, the saw must be secured in a stable position so that you can file safely and accurately. The Oregon Filing Clamp is a good example of a clamp that will hold the bar secure and completely stationary. The clamp can be held in place using the spikes.

The shortest cutter on the chain is the lead cutter and this is where you start filing. If they all appear to be the same length, start with any cutter but it helps to mark it so you know where you started.

4. Start filing

Position the file in the tooth which is the notch at the front of the flat chain link surface. Mount the file in the file guide and hold it at the correct angle, horizontally and vertically, as shown on the filing guide and/or stipulated by the manufacturer. Count your strokes and use the same number of strokes on each cutter. From this direction, you will be filing every other cutter.

File steadily using a moderate twisting action. Push the file from the short side of the angle. After every five or so cutters, you will need to move the chain and you will need to wear gloves for this.

With one side completed, turn the chainsaw around and work on the cutters that are angled the opposite way. You may want to check the length of the flat top of each of the cutters is the same with callipers to make sure that there is an equal "bite". The 4 inch Spring Caliper is a useful tool for ensuring consistent filing.

5. Use a depth gauge

The rakers are the hook-shaped links between cutters and they need to be checked with a depth gauge. One option is the Oregon Depth Gauge Tool. The depth gauge is positioned on the cutter. If the raker is higher than the ledge on the depth gauge tool, it needs to be filed down with a flat file.

Top Tips for Sharpening Chainsaws

  1. Never use a rattail file for sharpening your chainsaw. It has a tapered diameter and the teeth are coarse. This will destroy the chain’s cutters.
  2. Replace significantly damaged chains - they are never safe.
  3. The best option for holding the chain securely for filing is to clamp the bar into a vice but allowing the chain to rotate freely 
  4. You don’t always hold the file at a 30-degree angle. It must be at the same angle at which the cutter was ground initially. It could be 25 degrees so check the manual. 
  5. As you are filing, it is important that you count your strokes to make sure that the same number of strokes is applied to each cutter. 
  6. Always end by double checking the tensioning (be aware that newer chains will stretch significantly).
  7. You can sharpen the cutters on the chain multiple times before it will need to be replaced. If you find that the cutters are worn unevenly, you can take the chainsaw to a professional technician to get them reground into a uniform shape.