STIHL recommends having the cutting blades sharpened by a STIHL specialist dealer.
You can sharpen a hedge trimmer in two steps. First, use a flat file to sharpen the cutting blades. Always file in the direction of the cutting edge and adhere to the correct sharpening angle (see your operating instructions for the specific sharpening angle). Once you are finished filing, remove the burr that forms on the underside of the blade with a whetstone.
This video shows you how to sharpen your STIHL hedge trimmer.
Detailed instructions on how to sharpen your STIHL hedge trimmer are available in the operating instructions or from your local STIHL specialist dealer.