Turn on the chain brake and clamp the bar in a bench vice. Using a round file and a file guide, file each cutter using two to three steady strokes. Expose new metal, leaving the cutter faces shiny. When a metal burr exists on the edge of the cutter, sharpening is complete. Repeat this process for each cutter, disengaging the chain brake, advancing the chain, and re-engaging the brake as necessary.
If substantial metal is removed from the cutters, the depth guides may require adjusting or the cutters may not contact wood. Adjust the depth guides by filing them flat, just lower than the tooth behind them. Sharpening blades can also be completed using power tools. Common rotary cutters include small diameter grinding wheels and guides that can be used to sharpen chainsaws.
Use the grinding wheel by placing it against the cutters with light pressure. As with manual sharpening, the depth guides may also have to be lowered. In order to determine if a chainsaw requires resharpening, examine the wood shavings produced by the chainsaw. A sharp blade makes clean-cut chips, while a dull blade creates dust. Sharp chains cut faster and with less pressure from the operator and are less likely to kick back.