Not tried the Duragrit burrs but I am interested that Duncanh suggests that he's not too impressed with them. For piercing my turnings I use piercing cutters provided by Woodart Products. These come in a range of straight shanked sizes and in a limited range of other shapes..... Balls cones etc. Proxxon also have a reasonable range of TC burrs that have worked well and left a good finish. It is sometimes necessary to find the most effective speed to work theses sort of tools at. It isn't always the fastest speed that gives the best results.