Homemade Drill Bit Refurbishing Method

Hi Ric I'm not sure that you are aware, but drill bits are manufactured to a "nominal" size. They are by design, manufactured with a very shallow taper. For example, the 12mm drill I just measured (for this comment) is 11.98mm. It is tapered towards the shank, resulting in a size of 11.91mm. The drill is likely to bind if it did not have an inbuilt taper. It is NOT necessary to possess a drill doctor or drill sharpening machine to sharpen drills. I have been hand grinding my own drills since I was taught how to do so at school circa 1965. Sure, a drill sharpening machine will give more accurate results, but for most people and the "general" hole needs, hand grinding is suitable. Obviously it is necessary to grind as accurately as possible and this is not really too hard for most people. Some practice will help perfect the technique and their are tutorials/guide on the net on drill sharpening. In very general terms, drills do not have to be too accurate, as in most cases they are used in a drill press or powered/cordless hand drills. Having a pile of dull drill bits in a tub is not a "pile of junk" :-) it's time to have a sharpening session. When sharpening a drill bit, the included angle is NOT super critical and the length of the cutting edge is not critical. It is important though to make the angle and the length of the cutting edge equal on on both "sides" of the drill bit. The use of a micrometer for measuring drill bits is ok, but accurate results are obtained with digital calipers. I find that the best way to measure a drill bit is to place the calipers across the web and then slowly rotate the drill bit in "reverse". This will open the calipers to the actual drill bit size.