I recently discovered how to fix an issue with drilling that I was
having... I wanted to drill at a fairly slow speed in certain
materials and found that one type of bit worked best. Unfortunately,
they don't make that bit in letter sizes, which I need. Through
experimenting, I've realized that the reason why just this one bit
brand/type works so well, is how they designed the angle on the tip.
Not the point angle that is generally spoken of, such as 118 degrees
or 135 degrees... but the angle at which the tops are cut at. I'm not
even sure what you call that part of the bit. But if you look at the
bit from the side and see the main point, which is typically the
standard 118 or 135 degrees... then turn the bit to the other side and
look at the angle that goes along the top of that side... This is the
angle the controls how much bite the blades (if that what's they're
referred to) make into the material. I noticed that, that 'blade'
angle on the bits that work well for me are particularly flat compared
to most other bits... There's very little angle/bite at all. So... My
question is, does anybody know of a sharpener that isn't a fortune,
but can control that angle? Or is it possible to find human-beings
these days that actually know enough about sharpening to understand
that? I would like to sharpen numerous bits to that configuration.
Thanks for any info,
I'll bet somebody here has the wonderful instructions I once saw here. I think
it was by "T-Nut". In any case, learning how to sharpen your drill bits by hand
is worth the time and effort. The first step is to have a grinding wheel
dressed as close to perfection as possible. The rest is common sense and a bit
of practice. Don't over heat the steel! Once you learn the basics, you can
grind specials, like the one you mentioned with the low rake angle. You can be
an expert in an hour!
Another point to remember is all drills drill an over sized hole, or so
I was taught in machinist school. You can use this to your advantage by
doing it on purpose. It is accomplished by grinding one side slightly
longer that the other. Drill scrap to verify the finished hole size.
Sure you can. The trick is to grind and then drill a test hole and
regrind as necessary. Repeat until you get the required hole size. It's
an acquired skill and take practice, but it ain't rocket science.
Date: Mon, 11 Oct 1999 07:59:04 GMT
The drill was ground, freehand, on the FACE of the wheel (not the flat
side)...care being taken to keep the POINT angle as equal as possible
on both sides..I'll tell you how to do THAT in a moment..
Lets do that now in fact..
Jim, You are dead right about not being able to grind a drill without
mechanical help! Well here's how you create your own "6 Million
Dollar Bionic Darex"
Let's assume we are going to sharpen a 3/8" diameter, 2MT shank
drill..it is about 8" long (these figures are arbitrary..I just want
every one to have the same mental picture of what I am describing. We
approach the wheel, which has been dressed on its face, dead straight
across with no grooves..(Ve SHOOT anyone ve catch putting grooves in
ze drill wheel!!..No Pity..No Prisoners..Ya! Verdampt!)
The drill shank is held firmly in the RIGHT hand...ALL the movement
and control is imparted by the RIGHT hand. For the purposes of drill
grinding, the left hand could be...with benefit..a LUMP OF CLAY!!
It is from this "lump of clay" that we fashion the Bionic Darex".
Place your left hand thumb and finger tips LIGHTLY together..Relax the
other three fingers aand let them naturally curl against the palm of
Let the drill flute drop into the vee between thumb and fore finger
and let the tip of the finger "Find" the curve of the flute where it
fits comfortably. The tip of the thumb rests on the sharp junction ot
the land and the flute, about an inch back from the drill tip.
Now...SQUEEZE HARD!!! YOUCH!...I said it would be easier if it were
Lift the drill from your fingers...see the GROOVE?...Drop the drill
back in..it locates within a thou or two! Magic?..Bionic at least!
Squeeze again to set the groove. You have created a customised drill
guide that fits better that that on any machine ever built! You can
relax your grip now..feel how smoothly the drill will ride back and
forth, guided by the groove you have created for it.
Place the knuckles of your left hand, LIGHTLY on the ginding wheel
tool rest, and swing the drill shank, from left to right (using ONLY
your right hand) and push the drill lengthways though that groove in
your fingers back or forth using the groove to make the drill twist or
"rifle" in your fingers. Do NOT move your left hand in any way..it is
made of clay remember!
A) The drill axis is "eyeballed" to be at half the required point
angle to the wheel face...You can scribe or chalk reference lines on
your grinder benchtop to help you line this up..at least untill it
become almost second nature.
B) The drill axis is dropped JUUUst below horizontal. This will
ensure that your soon to be ground drill lip will start with a
"smidgin" of cutting clearance.
(Ideally, and certainly for a beginner, the grinder rest should be
set dead radially to the wheel center and about half the drill
diameter below the true center of the wheel)
C) The two cutting edges of the drill..the straight, sharp bits,
formed by the junction of the flute and the back face (the only bit
you grind), should be horizontally disposed..with the edge uppermost
on the side closest to your left hand..the othe sharp bit of course,
pointing downwards (Jeeze this would be a lot easier with a sketch
This I will call the SET or START position!
NOW, move your left hand for the first, last, and ONLY time during
this whole exercise. GENTLY ease the cutting edge towards the
spinning wheel, carefully maintaining all the angles and orientations
of the SET position..until the cutting edge is JUST shy of touching
the wheel. If you listen carefully you will hear the tone of the
entrained air, whistling through the narrowing gap.
You will hear a subtle but distinct change of tone JUST, I mean
Just...a couple tenths of a thou BEFORE the edge touches the wheel.
STOP!!! FREEZE!! DO NOT MOVE!!
Now, press the knuckles of your lump of clay..sorry, your left hand
FIRMLY down onto, into and around the grinding rest..establish a
"Groove" on the back of your hand as well as between your fingers.
We are now ready to grind, Your left hand locked to the drill and
grinding rest is otherwise quite relaxed..letting the drill slide,
twist and tilt wherever your right hand and the groove in your fingers
tell it to go.
The actual grinding is a bit of an anticlimax.
You have previously studied a new drill point, you have read about
clearance, and cutting angles, and rakes and......
With the RIGHT hand in control, gently, kinda, lean forward... bending
or squeezing your arms hands and body..rather than actually moving
them..until you take up that last couple of tenths and the wheel
begins to cut. Let it cut..don't force it, and dont' rush it..it
really won't hurt anything if you take a full minute Per pass per
face. YOU and your "Bionic Darex" are totally in control of that
drill and the wheel..Forget the times when, close to panic,
you swung the drill wildly past the wheel, hoping to get "the dirty
deed" over with as quickly as possible.
Take your time, enjoy the moment, THINK about the shape you are trying
to generate. Just the one face is left to "Interpretation"...every
other aspect,angle, facet, what have you...Has ALREADY BEEN TAKEN CARE
OF!! and is locked in place under your control!
The right hand should perfome a "Lower Quadrant sweep" for want of a
better term..An observer behind you would see your hand move from
about 17 minutes past the hour on a clock face, to roughly 25 minutes
past. But it isn't a smooth arc of a circle, more a sector of an
elipse..You see, as your hand starts to drop slowly, you are also
rotating the drill in "the groove"..the first third of the turn needs
to maintain that very slight clearance angle on the cutting edge,
and not increase it too rapidly.
You need the clearance to cut..But too much at that point will WEAKEN
the edge, and cause the drill to snatch and chip...So the first part
of the rotation is ALMOST but not quite, just as though you were
grinding a straight cone point on the end of your drill. Only as you
approach the second third, does your right hand start to noticably
drop..kinda "Catching Up" on the rotary motion...increasing the
clearance as it does.
In the last third of the rotaion the right hand drops quite
rapidly..Though not enough to catch the OTHER drill lip on the
wheel..that lip is coming around quite rapidly by now.
Above all, take your time, if it helps, move the drill one degree at a
time, and think ahead what shape or angle the next degree of cutting
face needs...Remember, you have control, and IT ain't going nowhere
'til you decide.
After a pass on one face, flip the drill in your "Bionic Darex" DO
NOT MOVE THAT LEFT HAND!!, return to SET position and repeat, the pass
on the other face.
Having done a couple of passes on each face..it is now time to check
the results on our homemade "Optical Comparator"
(Sorry Jim I couldn't resist!!) ;^)
Rest the center hole in back end of the drill shank, on the center
point of the "Comparator" and use, first one and then the other drill
lip to scribe a light line on your whitewashed (OK Blue or red dyed)
You will readily see if the lines coincide..if the lips are even..or
not, as the case may be.
Lets assume they are..Now look directly DOWN on the end of the drill
to check the clearances. HUH? How can you check radial clearance by
looking it straight in the face? Surely you need to look at it
Well no you don't...for once all thos interacting and confusing angle
and faces and clearances are going to work together in YOUR favor and
make what could be a tricky bit of metrology..quite simple. While we
are looking at the end of the drill, we will also check that the POINT
ANGLE is correct too!!!
(Ok guys, leave quietly..teenut has finally lost it!!)
No really, trust me. IF you look straight down on the point of a well
sharpened, standard drill, you will see the two cutting edges, joined
by the CHISEL edge which crosses over the web of the drill The angle
fromed by the chisel edge to each cutting edge, should be ABOUT 50
deg...anywhere between 40 and sixty is ok for a first attempt. (I can
hear the purists and theorists screaming and lighting up their flame
But believe me, get it in that ball park and your drill will CUT. If
the angle is too steep..you don't have enough clearance...negative
clearance will give you an angle event greater than 90 deg. Too MUCH
clerance and the angle will appear too shallow!
While looking at the end, check the point angle, How? Look down
the axis of the drill at the cutting edges. Are they straight? If
so, your point is pretty close to the right angle (As designed for
that drill, by its manufacturer when he set the helix angle and the
cross section of the flute) If the edges appear CONCAVE the point is
too flat and if they appear CONVEX, the point is too "Pointy"
If your drill passes all these tests, which take but a second or two
to perform, THEN IT WILL CUT..pretty close to size, without
chattering, chipping, overheating, wandering or seizing. I guarantee
Hey, thats a pretty good start for the first drill you ever ground!
All it takes now is a bit of practice for it to become second nature
and almost as easy with a little 'un or a big 'un!
My apologies for "goin'on" but If it helps just one person to pluck up
the couragre and go hand sharpen his (or Her) first drill, by hand...
Then I hope you will bear with me.
It is late, I am tired and I am not even going to proof or spell check
This post took a bit of cleaning up after all the extra linefeeds
added over umpteen computer systems. I hope I haven't botched it.
I use Teenut's system and it works for me. I usually pile up blunt
bits until there are about 50 of all sizes to sharpen, then do them as
a batch, the last is always much better than the first, so I usually
go over the first ten to improve them.
I think that all of Teenut's postings are archived somewhere. Does
anyone know where I can find them ?
I miss that man.
This is a fine article by teenut but I have said it before
and I'll say it again
now, switch RIGHT for LEFT and then it'll work as described!
my opinion and I'm sticking to it.........
I think that he's talking about a "dubbed" drill bit -- near
zero rake -- good for drilling in materials like brass and some
plastics. And this is normally done by hand after sharpening the bit in
the normal manner.
Email: < email@example.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
I took some bits to a local tool place that says he has a sharpening
guy. I labeled the one that works the way I need and told them to
match the 'lip angle' (if that's right). So we'll see. I gave them
just a couple to see if they do it right. Thanks for all the help
I was in Sears over the weekend with time to kill. They had several
models of Drill Doctor on sale at a significant discount. The 500 had
several features I didn't recall from the original model, and they were
sold out of the 750, so I couldn't see what sort of features it had that
would warrant the higher price. It looked like they had added several
adjustments to the 500, which could be good or bad. More stuff to fiddle
with & misalign, but in theory you can fix stuff you don't like.
Just out of curiosity, why not learn to sharpen the drill by hand? I
learned when I was 14 years old and it couldn't have been that complex
if a 14 year old kid with a different type of drilling on his mind
could master it -- sure wish I could have mastered some of those girls
I was thinking about :-)
(correct email address for reply)
On Tue, 15 Apr 2008 13:20:45 +0700, Bruce in Bangkok
It's pretty easy to learn how to hand sharpen a drill
and lots of advice on this has been posted.
BUT this can produce, at best, a drill that cuts well
and produces a hole that is oversize by a variable and
A drill can only produce its nominal size hole if the
drill point geometry is precisely symmetrical. It's reasonably
easy to come close to with a well designed drill jig but nearly
impossible with a freehand drill grind.
Can you gaze at your freehand sharpened drill point
geometry and be sure that your efforts have produced a point with
asymmetry less than 0.005"
Even this degree of asymmetry will produce a hole of
up to +0.010" on nominal.
On Tue, 15 Apr 2008 17:38:48 +0100, pentagrid wrote:
I'm sure the answer to that question is yes. 0.005" is easy to
see by eye. For example, if someone hands you a #11 and a #12
drill bit, about .002" different, you don't have any trouble
telling which is larger, do you?
On Tue, 15 Apr 2008 13:20:45 +0700, Bruce in Bangkok
As the high school shop teacher explained " you put the drill over
your left index finger resting on the tool rest and bring it up to
touch the wheel, then you just rock and roll it" (mid '50s)
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