FILENAMES: counter.jpg DESCRIPTION: This is a picture of a countersink tool. Posted by Ian Sutherland . The following description was provided: ================================================================= >Hi folks, I have a HSS 90 degree counterbore that I would like to >resharpen. It is a 90 degree cone on a shank with a hole bored through >the cone. I think the hole maybe at 90 degrees to the cone face. If >anybody can give me some idea as to how I might go about sharpening >it, I would be really gratefull (so would my neighbour who wants me to >sharpen 3 for him) I can possibly mount a Dremmel in the lathe tool >post & set the compound slide to 45 degrees, but I don't know how the >counterbore cuts, there must be some relief somewhere. In case my >descrption isn't clear, I will post a picture in photo's (when Iv'e >worked out how) & I'll label it as "Counterbore-Sutherland" If I can't >label it as that, I will repost with the address. TIA. Ian Sutherland. Just to clear things up, it's not a counterbore, it's a countersink. The type you refer to is called a zero flute countersink. They're used mostly for deburring. Close examination will reveal that the relief is an eccentric. It is produced with by an axial relieving fixture in which the countersink is guided with a cam. If the countersink is only going to be used for deburring and producing small chamfers, an acceptable regrind can be obtained by grinding the sides of the hole with a cylindrical wheel in a Dremel offhand. If an accurate wholesale regrind is necessary, you're better off sending them to a professional cutter grinder or tossing them and buying new.