Worked on tools to deburr spars. Die grinder still does not have enough horsepower after rebuilding compressor for enough CFM. So I worked with Roto Zip tool and other high speed rotary tools to find combination that removes enough material, none worked well enough. Burned up Roto Zip tool in process Finally arrived at 4" electric grinder with Roloc adapter and scotchbrite disk, works great! Using Die grinder with flap disk for lightening holes and 2" Roloc scotchbrite disks for fine work.