Before you decide what size chainsaw file you need for your chainsaw, first you need to determine the size of your chainsaw chain’s pitch. So if you have a large pitch for your chainsaw the cutting teeth will be higher as well. Commonly, chainsaw chain cutting teeth with a large pitch will require a larger file.
If you have a ⅜ pitch for your chainsaw chain, it is recommended that you use a chainsaw file with a size of 4mm for the pitch length to sharpen your teeth effectively.
How often you use a file to sharpen your chainsaw chain will depend on how often you use your chainsaw. Most professionals sharpen their chainsaw chains after around three hours of use so that the blades do not become dull for the next jobs. But the more you sharpen and maintain your chainsaw chains with a file the less likely you will need to replace your chain. However, if you rarely use a chainsaw, once a year should be enough.
In all there are four different sizes for chainsaw files.