[dwydendorf]

I worked 24 years as a tool and cutter grinder for a large automotive supplier. Don't waste your money on coatings. We did tool studies in our shop and the only tools that it worked on were end mills and shaper cutters. When you resharpen a drill, you have to take the drill back far enough that the corner is not rounded off. That means that if you look at the side of the drill, there is a small thin land that follows the twist in the drill. If that land is wide towards the front of the drill, you need to grind the drill back far enough to make it as narrow as the rest of the land. We used to have operators that would not run new drills without us resharpening them. That was because some new drills are not resharpened right. The foreign junk can be the worse, if you look at the end of the drill both sides should look equal, one side longer than the otherwill make it cut oversize. Typically you use black oxide drills on steel and bright finish drills on aluminum but either will work on the other. Most of the time the really expensive drills are not that much better, it is all in how they are sharpened. A Driil doctor works ok if you rough down the really worn drills first but I do most of my resharpening on a bench grinder. I also have an industrial machine to grind large drills.