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.