Joseph, I sharpen some of my burs often. But, it depends on what I
plan to use the bur for and how precise I need the tool to be. The
three rotary tools I resharpen most often are drills, larger hart
burs and knife-edge cutters. In a pinch I have sharpened krause
burs and cylinder burs but they are tricky and you may need to use a
relatively high magnification (10X) to cut precisely.
I use cutoff disks to sharpen. For drills, I do not modify the disk
at all, but for other burs, some modification is neccesary. Mount a
disk on a mandrel, place it in your flex-shaft handpiece and using a
diamond abrasive wheel or diamond abrasive block grind the disk
sharply so that the cutting edge on the circumference of the disk is
ground away. For sharpening burs I don’t use the outer cutting edge
of the disk (the circumference) to grind, as much as I use the side
of the disk. The disk must be cut sharply so I can grind precisely.
By cutting the disk an angle (basically removing the main cutting
surface) I can run the edge of the disk along the non-cutting edge
of the tooth and use the valley formed between the teeth as a guide.
With this method you are sharpening the tooth edge of the bur one
edge at a time, like faceting. Since you may have to grind 3 or 4
sides of a tooth, depending on the style of bur, you should devote
this process to larger burs only.
I don’t know if this was the best description of the process, but it
is the best I can do at 11:00P.M. the day before I leave for my
(hopefully) busiest show of the year. If there are any questions,
I’ll be glad to answer them when I get back.