Shop Made Drill Sharpening Jigs GadgetBuilder
End mills sometimes chip on the end of a flute and one way to continue using them is to make a small facet at 30° to 45° on the end of the flute (similar to the SPA on drills noted above). The result won''t cut sharp 90° corners but apparently lasts considerably longer than an acute corner so this is sometimes done deliberately during sharpening.