I have picked up 2 of those General drill bit jigs that mount next to
a bench grinder, I need to know
the best setup for sharpening my own bits. Ive got plenty of area,
several motors, arbors and
many different grit wheels. I read the drill doctor uses diamond
wheels, would this be better or if
not then what size grit and speed would be best? Ive even thought of
using one on a course wheel then one mounted on a fine grit & I could
even mount the motor/wheel flat like a turntable
and grind on the wheel face instead of the side.
Anyway I would like to know the best setup sense I will be starting
from scrach & change speed
wheel type & grit, angle ect.

On 2009-01-05, wrote:
I have picked up 2 of those General drill bit jigs that mount next to
a bench grinder, I need to know
the best setup for sharpening my own bits. Ive got plenty of area,
several motors, arbors and
many different grit wheels. I read the drill doctor uses diamond
wheels, would this be better

No -- it would not -- unless you are working *purely* with
carbide drill bits. Hot diamond combines with the steel to make a
harder steel, and dull the diamonds.

or if
not then what size grit and speed would be best? Ive even thought of
using one on a course wheel then one mounted on a fine grit & I could
even mount the motor/wheel flat like a turntable
and grind on the wheel face instead of the side.
Anyway I would like to know the best setup sense I will be starting
from scrach & change speed
wheel type & grit, angle ect.

Well ... what *I* like is no longer made. Dumore made a drill
sharpener sort of like the General turned on its side, with a built in
motor and a two grit compound stone -- a narrow part for the tiny bits
and a coarser one for the larger bits. (The thing would handle bits
from #70 up through 1/4" -- but no larger than that.

The bits were held in a special drill chuck, with a collet for
each size to steady it near the tip, aligned using a mirror and a
magnifying glass to have the flute edge orientation correct, and then
the grinding was done with a lever to slide the bit over from the mirror
to the wheel, and then you press down on a thumb lever to grind one
flute, then rotate the chuck 180 degrees (built to stop at the right
point) to grind the other flute.

I *would* like it to be able to grind split points, but it
can't, and neither can the General.

The Drill Doctor can -- only for the larger bits. Smaller ones
tend to come out as disasters unless you just go for the standard
point. :-)

Good Luck,
Don.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

Maybe I get a chance to offer you some advice now, DoN. I know it's my turn.

Split point drills aren't accomplished by gashing the second cut into the
back of the freshly ground cutting face.
They don't require a grinding wheel with a crisp 90 degree edge on it.

I've ground many sizes of split points by making the long ground facet at
the back of the flutes (trailing sides) first. These facets need to be equal
for both flutes.

Then the point is ground in the normal way, and the split points suddenly
appear, as if by magic.

It seems counter-intuitive, I know. I've mentioned this method here in RCM
at least several times, and not once has anyone said: hey, that does work,
so I suspect that anyone that read it assumed it wouldn't work.

What's there to lose by trying it? If anyone here doesn't have at least one
broken drill laying around, then break one and try it, or do it the next
time "someone else" breaks a drill.

It really is enjoyable to see it happen when starting with a broken drill,
because the finished drill is better than it was before it broke.

I learned this method many years ago when a friend gave me a couple handfuls
of used, quality drills with split points. When I first tried resharpening
them, I could see the points disappearing.
So then I started grinding the trailing side first, then the cutting face,
and the split points always remained prominent and sharp.

I'm sure there are optimum angles for the trailing edge grinds, but since
I've never had a Darex or other dedicated drill sharpening machine, I
eyeballed them (when the eyes were in better shape).
One industrial machine shop in a plant I worked in, had a Darex or something
similar, and grinding split points was done the same way I described, by
placing the drill holder in one hole first for the trailing grinds, then
touching up the cutting faces by putting the holder in another hole.

As far as fixturing for the trailing side facet goes, it could be a V in
front of the wheel edge, located at a low angle (that would be with the top
tipped toward the wheel from vertical) so the position of the web could be
seen when the drill is placed in the V.
The trailing side grind removes a considerable amount of material, thinning
the flutes.
Those are the two characteristics of split point drills, less flute width
and a smaller cutting face. They resemble the 4 facet grind at a glance.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"DoN. Nichols" wrote in message
...

No -- it would not -- unless you are working *purely* with
carbide drill bits. Hot diamond combines with the steel to make a
harder steel, and dull the diamonds.


Well ... what *I* like is no longer made. Dumore made a drill
sharpener sort of like the General turned on its side, with a built in
motor and a two grit compound stone -- a narrow part for the tiny bits
and a coarser one for the larger bits. (The thing would handle bits
from #70 up through 1/4" -- but no larger than that.

The bits were held in a special drill chuck, with a collet for
each size to steady it near the tip, aligned using a mirror and a
magnifying glass to have the flute edge orientation correct, and then
the grinding was done with a lever to slide the bit over from the mirror
to the wheel, and then you press down on a thumb lever to grind one
flute, then rotate the chuck 180 degrees (built to stop at the right
point) to grind the other flute.

I *would* like it to be able to grind split points, but it
can't, and neither can the General.

The Drill Doctor can -- only for the larger bits. Smaller ones
tend to come out as disasters unless you just go for the standard
point. :-)

Good Luck,
Don.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---