Put a separating disc in your flex shaft and cut the two faces of
the cutting edges at the same angle and same positioning as a new
A couple added notes to Marks description (which is dead on). I like
to use the super thin seperating disks (made in.006 and.009"
thicknesses. They're fragile, so handle them with care) The reason
is that they are made with smoother sides, so the face they cut on a
tiny drill is a bit smoother, slightly sharper, and the sides of
these disks cut very slightly slower, making it easier to control.
Second is that it can be tricky to get the two faces 180 degrees
apart, so they both get the same rake angle, which is important to
the drill working really well. Take care, before starting, to get a
good visual idea of where the flute is positioned. Usually, looking
from the side straight on where one is cutting that face, the
diagonal edge of the flute will be almost, but not quite, even with
the right hand vertical edge of the drill. This varies according to
how you're holding and looking at the drill. But examine that visual
picture before you start. Cut one face, then rotate the drill so the
second face makes that same visual picture. If your hands are holding
the flex shaft handpiece/seperating disk and the drill in the same
positions, then that second face will be pretty close to the desired
180 degrees apart. I also find it useful to hold the drill being
sharpened in a spare #30 handpiece. It's then easy to rotate the
drill 180 degrees, and looking at the positions of the chuck jaws
gives another cue to whether one is 180 degrees apart. Master that,
and then it's pretty simple to make sure the two faces you cut are
the same depth, same size, so the center cutting point of the drill
All this sounds complicated. It isn't. Takes maybe ten seconds once
you've got the drill mounted in that chuck or a pin vise (or your
fingers, if you're steady enough).
On drills that have been resharpened many times, and are getting
shorter, you'll notice that the center web gets thicker and thicker,
and the drill doesn't work as well. If you take a look at a larger
size industrial dril bit, which often have split points, you can see
that it's possible to extend that diagonal flute up into a second
small cut on each side, extending the cutting edge of the main flute
inwards toward the center web, thinning it again. For small jewelers
drills, it's much simpler than the larger geometry. Just a small
extra cut inside the diagonal groove with the edge of the seperating
disk, in the same diagonal direction. Again, simple enough once you
figure out what the hell I just described... :-)
Have fun. Oh, and don't forget eye protection when doing this.
Seperating disks can shatter, and you don't want bits in your eyes.
Usually, the optivisor will be enough, but I mention it anyway.