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.
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
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
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.
That is the tricky part -- since nothing that I have is set up
for that. I don't see a way to set up the DuMore for that, either, and
working on the smaller bits (1/8" on down) would be pretty tricky.
O.K. That sounds reasonable.
I don't remember seeing it -- perhaps you posted it late enough
into a thread so I had stopped following it -- especially likely if the
thread split into political without a change in "Subject: " header. :-)
When I have to sharpen a large enough bit to do most of it by
hand, I will try it. But I seldom use larger bits, so don't hold your
And the only Darex I have has been abandoned by them -- the
original "Drill Doctor" which does not have that kind of adjustability. *That* tool is what I would love to have.
Hmm ... perhaps modify the roughing post on the DuMore, designed
for taking most of the work out of sharpening a broken bit, so the
expensive and difficult to find compound wheel does not get worn as
And what *is* the difference? I thought that it was just a
matter of what the maker chose to call it.
I am not overly impressed with the split point produced by the Drill
Doctor 750. It cuts the trailing edge back too far, to the point that
to re-sharpen again, you must grind the drill back and get rid of most
of the previous splitting grind. Another problem is that the splitting
grind goes past the centerline - can be corrected by adjusting the
longitudinal position of the diamond wheel slightly.
I think the difference between split point drills and the 4 facet grind is
that the 4 facet method is just 4 flat grinds, there isn't and crown in the
cutting face relief, and without split points, there is still the small
chisel edge at the web.
In all the years/decades of developing drill sharpeners, the tooling
companies haven't come up with a decent drill sharpener that's affordable
for the part-time tinkerer/home workshop users.
Some Drill Doctor owners will probably argue that, but I've read the
complaints of many stating it works OK some of the time, on certain sizes.
I don't like the little General fixture mentioned earlier, because the
little twist indexing finger isn't a good feature. That's the little pointy
adjustment located under the V (only the worst place for it).
The little General fixture makes a great relief grind as it swings, but it
will make it anywhere on the end of the drill. So ya play and adjust and try
a few grinds, then play and adjust some more until it's leaving the
narrowest chisel point, but ya start over as soon as you try another size
Besides that problem, the only sensible way to mount the General fixture is
on a slide or a mount that allows it to be moved toward/away from the
grinding wheel and held in place. Bolting it to a fixed point as suggested
in the instruction sheet, sucks.
I'm fairly certain that you already realize the basis of these comments DoN,
but I'll add them FWIW.
As the point is ground, the angular rotation of a drill needs to follow a
fixed point on the fixture that has a relationship to the twist spiral. Just
moving a drill toward the grinding wheel without following the twist will
change the orientation of the chisel point.
If the fixed point on the General fixture was on top where it could be
adjusted easily, that would be tits.
With a conventional grind on a drill, maintaining the narrowest chisel point
(at the web) is the key to having a drill that cuts and feeds easily, and a
drill that may only rub a hole in something if enough pressure can be put on
The key to attaining the narrowest web/chisel point width is a fixed point
that causes the advancement of the drill to follow the twist.
A while ago, someone was looking for the identity/maker of a drill grinding
fixture that was made by Delta (Rockwell/Delta, maybe). It was a couple of
arms and a few adjustments with scales which takes up quite a bit of space
just to mount the fixture.. considerably more than a sqare foot of space,
not including the bench grinder it gets mounted to. You probably need a
workspace about 24" square to operate it.
I have one that's similar to the Delta that was made by Kalamazoo, but I
haven't used it yet, since all my stuff is waiting for me to locate a new
It's got a long sweeping arm and a scale or two, but I suspect that it's
performance will depend upon some futzing around too.
It's beyond me why some tool maker hasn't developed a drill sharpener that
is as easy to use as zing, rotate, zing for the trailing side grinds, then
insert, rotate, lift, rotate and it produces a resharpened drill that as
good as factory fresh new.
Beyond me, besides the fact that there aren't many small tool manufacturers
That's all the motion that the machine shop drill grinder needed to produce
perfect split point grinds.
I realize that a single drill holder won't suffice for all the sizes up to
3/4", it's just not realistic, and a large portion of the value of a real
drill sharpener would be in the precision drill holders.
I've pondered how to make a round drill holder resembling a drill chuck for
quite a while, and haven't come up with anything better than modifying a
drill chuck. Snugging the chuck jaws against the drill flutes could cause
chipping, so gripping the shank would likely be a better approach.
Supporting the drill near the point presents another challenge, since
bushings for every drill size would be problematic as far as time consuming
to make and/or expensive to buy. Something like a camera lens iris might be
If large drills are to be resharpened, then a small drill chuck would need
to be adapted/adaptable upward in size to fit in the same place as the big
That's what I've read repeatedly, Gerry. Various little problems, but
overall, a somewhat useable machine.
But if it only sharpens some sizes consistenly, that reduces the number of
different fastener sizes that one needs to buy.
I suspect that some of the problems are a result of too much plastic being
used to make them.
I once ground mine away and made a new one but I have binned it!
The destructions suggest rotating the drill until the helix is in
contact with the finger. Experience has proved that this is wrong
IMHO. When I use the General I rotate the drill until the cutting edge
is vertical by eye and clamp it there. Once the first land is ground I
leave the setting where it is and rotate the drill until the second
land is again vertical
The destructions are reasonably valid with regard to overhang etc but
you do need to adjust the jig in and out as you note below.
My fixture has a slotted base!
One other point, the grinding position as shown in the instructions is
non preferred IMHO. Better to grind on the wheel face above or below
the spindle. That way the grind is perpendicular to the edge.
I must say I rarely use my jig.
1 I can grind by hand adequately
2 My drills last a long time primarily because I load them and keep
them cutting. A colleague once said when he saw me drilling some steel
with a hand power drill "you don't drill holes you punch them".
Interesting that my drills were never changed or sharpened but his
were always needing replacing
Looking at a General No. 825 from the 60's, if the pivot for the hold-
down clamp was moved further outward to reduce its angular rotation, a
'billet' clamp could include a top finger. Unlike the bottom one the
contact point would shift lengthwise with drill diameter.
The original Drill Doctor works well enough for me, but I've also been
considering putting the General fixture on the surface grinder to use
its XYZ motion, and making a sleeve that fits onto Darex chucks with
an alignment wire or plate across the end.
I use a small parabolic drill first to avoid fussing with split
Bison makes 6 jaw chucks for tool grinding. Not Cheap!!
The Darex chucks aren't bad as long as you don't tighten them more
I made this 5C collet nut for sharpening large drill bits in an end
mill grinding fixture:
The 1/2" insert centers S&D drills by the shank. The back relief
setting grinds a 120 degree point. A long bit will clear the side of
the mag chuck while the base is on the poles. I've been downstairs
trying it and clearly need to make a spanner wrench to tighten the
The General-type drill fixtures I've got have a slotted base too, Richard,
but loosening the nut/bolt will allow the base to rotate, so that's just
more futzing around with adjustments.
I agree with your comments regarding the instructions, like many instruction
sheets, they didn't get it right.
And like many little handy helper devices, just a little more design work
would've made a great little drill grinding fixture that almost anyone could
set up and get very good results with very little effort.
Very good lighting, properly placed near the work area is a requirement for
sharpening by hand. I used to be quite good at it, but now even with 3 or 5
diopter magnifying lenses, the results aren't as good as when I was using my
20 year old eyes.
This is where a fixture that indexes to the twist, and has two locations 180
degrees apart would greatly simplify resharpening, without even seeing the
I also agree with your comment regarding agressive feed rates and grinding
on the wheel face, not the side. When a drill is sharpened properly, there
is no reason not to push the feed, using a good cutting lubricant.
Nice job on adapting the endmill grinding fixture, Jim.
For others that might be following along, the General-type fixture has been
available for decades, and one of mine is a Craftsman, but they're still
being made.. and copied, presumably in China sweatshops for the tool
Those Bison chuck prices range from almost $100 to over $100 per inch..
ouch, that's just extravagance for a hobbiest.
Your modification recommendation for the clamp on the General fixture would
be a very good addition.
I have a couple of these "General" fixtures and have been thinking of
setting one up in conjunction with my 4 1/2" angle grinder as a
roughing sharpener then finishing on my Drill Doctor. Somewhere in
connection with this group I have seen picture of an adjustable mount
for the "General" fixture where it is moved on round rod ways by means
of a lead screw arrangement.
O.K. That sounds reasonable.
[ ... ]
I've seen posted descriptions of a slide mount for the General
You might look at the design of the (sadly now discontinued)
drill sharpener once made by DuMore.
Check out the manual at:
note that it is a PDF file, and one made from scans of a photocopy of
the manuals, so it will be easier to read if you download it first, and
look at it (or print it) later.
I got mine in old and rather incomplete form, so here is what I
did to get it back to usable shape:
It does not do a split point, but it does do a nice job all the
way down to #70 bits.
[ ... ]
Pretty close to that with the DuMore -- especially when handling
the larger bits (up to 1/4"). The smaller bits are harder to see to
line up properly using the mirror and reference edge. It really needs a
microscope instead of the magnifying glass.
That is part of the problem. The cost of good drill bits brand
new is low enough to make the number of purchasers of a good sharpening
fixture somewhat low as well.
Well -- what about a nylon jawed chuck? You would need
several sets of jaws to cover the full range of sizes given the wear
that the larger sizes would experience.
The DuMore grabbed the shank, and used fixed size collets for
each size of bit. The collets were secured by a thumbscrew, and easy to
change, and could easily be made in quantity on an automatic screw
machine. A lot easier (and cheaper) to make than a set of collets like
the ER series collets.
It used a specialized drill chuck (three rubber flex joined
jaws) which used to be used on much older 1/4" electric drill chucks.
Unlike the electric drill chuck, which was tightened by screwing onto
the shaft, this one has a large knurled collar to close the jaws. The
chuck fit in a holder which allowed precisely 180 degree rotation, so
you set the bit properly for one flute, and when you have ground it, you
rotate the chuck in its holder to position for the second grind. That
part is quite rapid.
Probably what killed the product is the discontinuation of that
style of drill chuck and the resulting drying up of the source of the
A normal key type or good Albrecht style keyless chucks are a
bit too big in diameter to fit the 180-degree collar -- and don't have
the pass-through feature which is needed.
I later got an almost complete set of the collets, with the
fitted box. I could make the few extras needed more easily than a
complete set from 1/4" to #70 including fractionals from 1/4" down,
number size from #1 down to #70 (skipping #71-#80), and letter size from
'F' down to 'A'.
The problem with an iris is the limited space around the tip of
the drill bit while it is swung for the grind. The collets are probably
the most reasonable approach.
The bushings (collets) were of a design which would be very easy
to make with an automatic screw machine.
The sharpener covers a wide range of point angles, and does
adjust the spacing appropriately.
You would need a much larger wheel and overall system to grow
the DuMore approach to larger sizes. Probably 4' by 2' of bench space
for a 3/4" drill.