I have a Stihl straight shaft trimmer that I use for everything around my 5 acres, including using a blade to cut down buckthorn saplings. The blade has become dull and despite the guidance from Stihl that it needs to be professionally sharpened, I'm trying to figure out if I can sharpen it myself. Has anyone sharpened a blade like this? https://www.stihlusa.com/products/t...ers/trimmer-heads-and-blades/circularscratch/ I called the dealer that I bought it from and they can't sharpen it. Thanks!