Forstner drill sharpen with nail file
Forstner drills - also called pot drills - are important helpers. They drill precisely, whereby the borehole is also used as a clean rounding contour for cutouts or penetrations. I do not need that often. And that means of course to provide sharpness. But that is actually real professional work and therefore not very cheap.
Temporary remedy creates the good old (diamond coated!) Nail file. You put them flat as shown in the picture and start digging. It works amazingly effective. Old nail files are very helpful, even when it comes to quickly removing burrs and sharp edges, both in metal and in ceramics and glass. So do not throw it away!