We've been using DeWalt 10mm Extreme 2 HSS Drill bits ( Screwfix 32213), they're 10mm drills with the points thinned to a pilot of about 4mm and the hole then cut to full size by chisels on the flanks of theses, like a pilot drill and plug drill combined into one. They are hard but brittle and not cheap. I'm going to have to try sharpening them but wondered if the hardness is likely to be a small depth such that they won't stand much sharpening? The flanks have become chipped rather than worn blunt, from drilling palisade fensing on site.
I'm guessing I'll need an ordinary drill guide to sharpen the pilot and a dremel to do the chisel edges or are there better suggestions?
AJH