Huh! I sharpen drill bits on my grinder too. Sometimes I get a good
cutting bit, other times I get a good scoutmaster's fire starter or a great
oval-cutter! This just may help with a little of that trial and error
business I'm so famous for.
I'm gonna put this up over my drill press for next time I need it. Now
if I can only figger how to get that danged point to CENTER :-)!

Good writeup;

Pop`
--
Wrong does not cease to be wrong
because the majority share in it. Tolstoy



Bill in Detroit wrote:
RayV wrote:

Unless I'm missing something doing it that way would give me the same
results as the grinder jig and probably the DD too.


After about the third snapped drill bit I think you'll give up on this
idea. Moreover, as another poster has mentioned, you will be grinding
a cone and a cone can't cut. Period. Not at all.

So let's get you trained to sharpen drill bits by hand so you can
amaze your friends, confound your enemies and have a lifetime supply
of sharp drill bits at your beck and call.

____________________________

Let's start with a two-flute, 118 degree twist drill. No carbide,
nothing fancy at all. It's what you get when you pick up that Vermont
American blister pack down at the local hardware store.

Looking straight down at a new common twist drill bit, you will see
that the end is made up of three straight lines: two cutting lips and
a chisel wedge in the middle. That is, in fact, what each of these
edges do.
Notice that the chisel is centered between the two cutting lips.
That's where it NEEDS to be. If its off-center, so are the cutting
lips and all bets are off so far as the resulting hole geometry.

Now look at the drill bit sideways. Notice that the line running
(mostly) horizontally from the edge of each of the cutting lips
actually tilts down and to the left a tad. This is the cutting relief
angle and controls how thick the waste can be. Low angle, slower
drilling, stronger lip. High angle, faster drilling, weaker lip. The
relief
angle, also, benefits from being equal for each side although the
rate of penetration is limited by the shallower side so 'close enough
is close enough' (get close, but don't be obsessive about it.

To sharpen:

Dress your grinding wheel flat. Don't even think about skipping this
step. If you don't do it now, you will in a minute as soon as you see
what your drill bit does when bouncing off an out of round wheel while
trying to sharpen a straight edge against a circle with a groove in it
and chunks out of it.

Holding the drill bit up to the wheel, angle it so the shank is to the
right (for the most common twist ... a right hand spiral). Hold it so
that the edge is horizontal. This means that the shank will be dropped
backwards to compensate for the lip angle.

JUST BARELY touch the lip to the stone to confirm that the stone is
smooth and the drill bit is touching across the width of the cutting
lip. Match straight line to straight line. If the drill bit isn't
straight across, balance out the curve. If the wheel isn't straight
across, you didn't do what I told you to in the very first step. Stop
right now, go back and follow the directions. Sharpening drill bits is
pretty easy if you don't try to take shortcuts. If you DO try to take
shortcuts, it's darned near impossible to do a good job ... more so
when first starting out.

Now, with light pressure (until you get a feel for the results) rub
the drill bit against the wheel while simultaneously 1) applying
increasing pressure (this will become your relief angle ... just
about 3-5 degrees is plenty to start with) and 2) rolling the bit
between your fingers while lifting the tip upward. This is the
'skill' part. You need to make these two motions in concert with each
other so as to end up with a tapered cone / flat spiral that starts
with the cutting lip and drops back slightly at the back of each
flute. This is the part your jig could not do.

Now check to see how you did on this first lip. Be critical of your
results. No slack. It probably looks horrible. See that flat spot
right at the lip and that grind mark on the other lip where you
didn't pull away from the stone in time? That's about par for the
course. If it doesn't look like this, chalk it up to either lax
standards or beginners luck. Experienced people will sometimes get
these marks if it has been a while since they had to sharpen a bit.
The key is to hold yourself to high standards and not quit until you
achieve them.
Try again on the second lip. When you check the second lip, also look
at the drill head on to see if the chisel is centered. If it isn't,
re-grind the longer of the cutting lips, being certain to duplicate
the angle on the shorter lip.

It is a good idea to have a water cup handy to quench / cool the tip
after each pass over the grinder. HSS air hardens so we are not too
concerned about the hardness of the steel, but ARE concerned about
your ability to hold a piece of hot metal in bare hands. If it's too
hot to hold comfortably, it's too hot. Cool it. It's a good practice
to cool it after every pass over the wheel but if you are making
light cuts, you may get a couple passes in before things get
uncomfortable.

You can buy a cheap drill gauge at pretty much any tool outlet store
... the General brand is as good as any ... which is to say that none
of them are anything more than approximate. Or you can use a pocket scale
(machinist term for ruler) with fine gradations of at least 1/32 to
measure the cutting lips (when they are the same, the wedge is
centered) and the relief angle (hold the scale horizontally and check
to be sure that the relief is the same -by eyeball- for both flutes.
A protractor with a long arm (again, the General brand is fine) will
help you determine the precise included angle of the lips. To use the
protractor, align one edge with the shank of the drill and the swing
arm with the cutting lip. It should be half of whatever angle you are
looking to make AND the lip should be straight from corner to corner.
Profile it against a good source of light.

Gotchas:

Make certain NOT to round off the corners of the cutting lips. No
matter what the rest of the lip looks like, if the corners are
rounded, the drill is dull. If the corners were rounded during use,
continue grinding until you get past them while meeting all the other
conditions above.
Make certain NOT to grind a flat at the cutting lip ... it MUST be the
highest point on the flute. That is, if it is flat, it will rub, not
cut. If it is flat and the other lip is good, you now own a 1-flute
drill which will cut ovals for you. For a while.

You will probably be able to sharpen drill bits down to about 1/8"
using this method. Below 1/8" things get iffy quickly so your best
bet may be to simply purchase a new bit.

Nota Bene:
If you snap a good-sized drill bit (oh, say, somewhere north of 1/4"),
grind the shank off and then, while chucked in our drill press or
lathe, grind a cone on the end. This simple device is useful for 1)
marking where a drill bit will enter work on the drill press or 2)
for hand tapping on the drill press.

To hand tap on the drill press, first drill a hole to the proper size
for tapping then, without moving the workpiece, insert the tapping
center you just made into the chuck. Then place the tap and handle
between the workpiece and the tapping center. Many taps and T-handles
have a recess precisely for this purpose. Then apply light pressure to
the drill press quill while turning the tap with the other hand.
Voila! A perfectly vertical tapped hole!

If the workpiece gets nudged before you can get everything set up, use
the tapping center to re-locate it ... a hole will locate precisely
on a cone.



When I first entered the machine trades I was given a thread gage and
100# or so of mixed bolts to sort. I can tell metric from English and
the various sizes and thread in each group by sight to this day ...
and I haven't worked as a machinist for nearly 10 years.

Right after that I was given about the same weight in dulled drill
bits to sharpen ... and one good drill bit to copy. Total instruction
consisted of "Hold the drill bit about like this ... move it in an arc
about like this. Make it look like the good one. There ya go. Have at
it. Let me know when you think you've got the hang of it."

So practice, practice, practice. And let us know when you think you've
got the hang of it. ;-)

Bill

BTW, to make a flat-bottomed hole similar to one made by a Forstner
bit but without the dimple in the bottom, startb with two drill bits
the same size. Leave one as-is and grind ALL the cone part off the other
one then grind the cutting lips back to get rid of the middle wedge
and then grind a back relief behind the cutting lips. Set your drill
press to make a hole to the finished depth with a regular drill but leave
maybe
1/32 or 1/16 of material in the bottom of the hole. The resulting hole
will have straight sides tapering to a point in the middle.

We are going to cut off the tapered part (only) wqith the flat-bottom
drill.

Now change to the flat-bottom bit and reset the drill press to the
FULL depth. With the press off, Lower the flat-bottom drill bit into
the hole to re-locate it. Then turn the drill press on to the same
speed as foir the first bit and finish the hole.

You can pull the same stunt with a tap to tap all the way to the
bottom of a hole. Just keep in mind that when the tap hits bottom
it's time to stop turning it unless you get some sort of perverse
kick out of digging broken taps out of mangled holes. To each his
own, I suppose. :-)
Each trade has its tricks. I've been a machinist. Now I'm learning
woodworking.