From time to time I have had real trouble sharpening SOME drill bits on
my Darex Drill Doctor. I thought I understood it pretty well.

As others have done, I have 2 complete indexes of "Import" bits. I use
them for general work, always replacing them with high quality bits when
the originals fail. (surprisingly, some of the larger sizes do seem to
hold up pretty well).

A couple of days ago I had to drill a couple of #16 holes in some
pretty hard steel, the tang of a knife. First I grabbed a Chinese bit
and it dulled real fast. Then I grabbed a USA HSS dril bit. It drilled
one of the holes and part way through the other before heating up and
dulling.
When I took the Chinese bit to the Darex, I noticed that it was badly
dulled and I couldn't get the angles right. Somehow, it just didn't
look right down in the Drill Doctor cavity where the two little fingers
grab it. I tried several times, but no luck.
The HSS bit sharpened right up with correct angles and I completed
the job for my friend.
After he left, I tried to figure out why I couldn't seem to get the
Chinese bit to sharpen correctly. Finally, I realized that the back
of the "land" had less material in it than the USA bit. These Chinese
bits even feel funny when held in the hand. They feel "skinnier" in
back of the actual cutting land.
This causes the grinding angle to be off a LOT when you transfer the
bit from the locating port to the grinding port. I tried to rotate the
locating collar CCW, but I gave up after several tries and just hand-
sharpened it.

I checked several bits and see the same sort of problem, at least with
the smaller bits, but in no way do I have enough data to tell how
extensive the problem might be.

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

I'd be interested to hear from others who have had similar experiences
or could shed light on the problem.

Pete Stanaitis
--------------------------------------

spaco wrote:
From time to time I have had real trouble sharpening SOME drill bits on
my Darex Drill Doctor. I thought I understood it pretty well.

As others have done, I have 2 complete indexes of "Import" bits. I use
them for general work, always replacing them with high quality bits when
the originals fail. (surprisingly, some of the larger sizes do seem to
hold up pretty well).

A couple of days ago I had to drill a couple of #16 holes in some
pretty hard steel, the tang of a knife. First I grabbed a Chinese bit
and it dulled real fast. Then I grabbed a USA HSS dril bit. It drilled
one of the holes and part way through the other before heating up and
dulling.
When I took the Chinese bit to the Darex, I noticed that it was badly
dulled and I couldn't get the angles right. Somehow, it just didn't
look right down in the Drill Doctor cavity where the two little fingers
grab it. I tried several times, but no luck.
The HSS bit sharpened right up with correct angles and I completed
the job for my friend.
After he left, I tried to figure out why I couldn't seem to get the
Chinese bit to sharpen correctly. Finally, I realized that the back
of the "land" had less material in it than the USA bit. These Chinese
bits even feel funny when held in the hand. They feel "skinnier" in
back of the actual cutting land.
This causes the grinding angle to be off a LOT when you transfer the
bit from the locating port to the grinding port. I tried to rotate the
locating collar CCW, but I gave up after several tries and just hand-
sharpened it.

I checked several bits and see the same sort of problem, at least with
the smaller bits, but in no way do I have enough data to tell how
extensive the problem might be.

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

I'd be interested to hear from others who have had similar experiences
or could shed light on the problem.

I have seen cheap drill bits with proportions
that just didn't look right. I suspect it's
the same issue as you found.

spaco wrote:

From time to time I have had real trouble sharpening SOME drill bits on
my Darex Drill Doctor. I thought I understood it pretty well.

As others have done, I have 2 complete indexes of "Import" bits. I use
them for general work, always replacing them with high quality bits when
the originals fail. (surprisingly, some of the larger sizes do seem to
hold up pretty well).

A couple of days ago I had to drill a couple of #16 holes in some
pretty hard steel, the tang of a knife. First I grabbed a Chinese bit
and it dulled real fast. Then I grabbed a USA HSS dril bit. It drilled
one of the holes and part way through the other before heating up and
dulling.
When I took the Chinese bit to the Darex, I noticed that it was badly
dulled and I couldn't get the angles right. Somehow, it just didn't
look right down in the Drill Doctor cavity where the two little fingers
grab it. I tried several times, but no luck.
The HSS bit sharpened right up with correct angles and I completed
the job for my friend.
After he left, I tried to figure out why I couldn't seem to get the
Chinese bit to sharpen correctly. Finally, I realized that the back
of the "land" had less material in it than the USA bit. These Chinese
bits even feel funny when held in the hand. They feel "skinnier" in
back of the actual cutting land.
This causes the grinding angle to be off a LOT when you transfer the
bit from the locating port to the grinding port. I tried to rotate the
locating collar CCW, but I gave up after several tries and just hand-
sharpened it.

I checked several bits and see the same sort of problem, at least with
the smaller bits, but in no way do I have enough data to tell how
extensive the problem might be.

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

I'd be interested to hear from others who have had similar experiences
or could shed light on the problem.

Pete Stanaitis
--------------------------------------


This is a problem that is as old as the drill doctors.

It comes down to being a failure to be willing to experiment in spite
of the results of following the instructions, several times in a row,
not working out.

Drills are different. Experiment. Twist the drill forwards or
backwards from the setting suggested in the instructions and look at the
results.

If you bought a $5000 sharpener, you would still have to deal with
variables in different manufacturers drill bits.

Check The Drill Doctor site. There was a run of the early ones that
had some issues. They had a recall, or at least were trading in the old
ones. shrug A bud had one of the old ones when it was new. If you
folowed the instructions exactly, and refused to deviate from them, it
either worked or it did not. If you looked at the drill bits, and mad e
adjustments as required, as indicated by the results, it worked very well.

Adapt! :-)

Cheers
Trevor Jones

On 2007-12-12, spaco wrote:
From time to time I have had real trouble sharpening SOME drill bits on
my Darex Drill Doctor. I thought I understood it pretty well.

[ ... ]

After he left, I tried to figure out why I couldn't seem to get the
Chinese bit to sharpen correctly. Finally, I realized that the back
of the "land" had less material in it than the USA bit. These Chinese
bits even feel funny when held in the hand. They feel "skinnier" in
back of the actual cutting land.
This causes the grinding angle to be off a LOT when you transfer the
bit from the locating port to the grinding port. I tried to rotate the
locating collar CCW, but I gave up after several tries and just hand-
sharpened it.

I checked several bits and see the same sort of problem, at least with
the smaller bits, but in no way do I have enough data to tell how
extensive the problem might be.

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

I'd be interested to hear from others who have had similar experiences
or could shed light on the problem.

Hmm ... I do know that the settings on the tool assume a
standard helix on the drill bit. A fast spiral or a slow spiral will
not be properly aligned. And even worse, the straight flute bits which
used to come with the Yankee pump screwdrivers and drills.

The drawing of the end of the bit looks like you have a straight
flute bit, but it could simply be that it is a strangely shaped groove
in the flutes.

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 ---

spaco writes:

I checked several bits and see the same sort of problem, at least with
the smaller bits, but in no way do I have enough data to tell how
extensive the problem might be.

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

That's interesting. I have the 350X Drill Doctor, the newest low-end
model. It does not locate bits in the chuck using an alignment gadget
built into the body like older Drill Doctors. Instead, there are a
pair of locating fingers that are part of the chuck itself, and you
manually rotate the drill so that the side cutting edges (the forward
sharp edge of the flutes) touch these fingers.

It seems that this might locate the drill more accurately, because the
missing "land" areas you show are not used for anything. I wonder if
this redesign was partly motivated by such nonstandard drills.

(The new method has its problems too - it's hard to align drills at the
low end of the chuck's gripping range.)

Dave

Thanks, Dave.
That's a good piece of info!

Pete Stanaitis
---------------------------

Dave Martindale wrote:
spaco writes:


I checked several bits and see the same sort of problem, at least with
the smaller bits, but in no way do I have enough data to tell how
extensive the problem might be.


I put an image of a drill bit on my website to try to show this problem.


Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.


That's interesting. I have the 350X Drill Doctor, the newest low-end
model. It does not locate bits in the chuck using an alignment gadget
built into the body like older Drill Doctors. Instead, there are a
pair of locating fingers that are part of the chuck itself, and you
manually rotate the drill so that the side cutting edges (the forward
sharp edge of the flutes) touch these fingers.

It seems that this might locate the drill more accurately, because the
missing "land" areas you show are not used for anything. I wonder if
this redesign was partly motivated by such nonstandard drills.

(The new method has its problems too - it's hard to align drills at the
low end of the chuck's gripping range.)

Dave

On Wed, 12 Dec 2007 15:16:46 -0600, spaco wrote:

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

I'd be interested to hear from others who have had similar experiences
or could shed light on the problem.

Pete Stanaitis
--------------------------------------



Not a bad drill bit.. a bad drill bit sharpener. That form is common in roll
forged twist drills. Normally found in larger sizes though.


Mark Rand
RTFM

On Thu, 20 Dec 2007 23:10:09 +0000, Mark Rand
wrote:

On Wed, 12 Dec 2007 15:16:46 -0600, spaco wrote:

I put an image of a drill bit on my website to try to show this problem.

Go to:
http://www.spaco.org/BadDrillBits.jpg
The RED areas show where, IMO, metal is missing from the back side of
the land area.

I'd be interested to hear from others who have had similar experiences
or could shed light on the problem.

Pete Stanaitis
--------------------------------------



Not a bad drill bit.. a bad drill bit sharpener. That form is common in roll
forged twist drills. Normally found in larger sizes though.


Mark Rand
RTFM

The "land" is relieved to reduce friction on the bit - think 2 inch
drill bit.

I don't understand the discussion regarding "drill sharpeners" can't
you sharpen a drill by hand? One of the first things I had to learn in
my apprenticeship was how to sharpen a drill bit.

Bruce-in-Bangkok
(Note:remove underscores
from address for reply)