Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst

--Next time you might try lubricating with Moly Dee. Also I've found
cobalt drills are best on things with surface hardness like stainless
stampings, as opposed to right-thru hardness like what you're up against.
For those situations maybe you're better off with carbide drills?

--
"Steamboat Ed" Haas : Do us a favor and rescue
Hacking the Trailing Edge! : a doggie or three...
www.nmpproducts.com
---Decks a-wash in a sea of words---

On Sun, 4 Jan 2009 08:38:33 -0800 (PST), Ernst
wrote:

Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst
-------------
There are cobalt bits and there are cobalt bits. From personal
experience and the many postings in these news groups it is
apparent that "Craftsman" quality has slipped in the past few
years. You may want to try some name brand cobalt drills from a
mill supply.

Another consideration is that the cobalt bits are not necessarily
"harder" than HSS (although they are more brittle) but the cobalt
provides higher heat resistance allowing higher RPM and faster
drilling, which may be important in a production environment.

If you have a very rigid setup [good fixturing, good spindle, and
a steady hand] carbide drills may be "better" as these are
definitely harder than HSS. These are also much more expensive,
difficult to resharpen, and are *VERY* brittle and prone to
breakage at the slightest provocation.
for example
http://www.use-enco.com/CGI/INSRIT?P...MPXNO=19499422
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
There are special "die" drills for very hard workpieces.
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32

Unless speed of production is an important consideration, the
total tooling cost may well be lower with good quality HSS
drills, slow(er) speeds, and lots of HD cutting oil.
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32
http://www.use-enco.com/CGI/INSRIT?P...PARTPG=INLMK32


There are many other good brands/suppliers available, I used Enco
just as an example.

Let the group know what you settle on.


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

"F. George McDuffee" wrote in message
...
On Sun, 4 Jan 2009 08:38:33 -0800 (PST), Ernst
wrote:

Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst
-------------
There are cobalt bits and there are cobalt bits. From personal
experience and the many postings in these news groups it is
apparent that "Craftsman" quality has slipped in the past few
years. You may want to try some name brand cobalt drills from a
mill supply.

Another consideration is that the cobalt bits are not necessarily
"harder" than HSS (although they are more brittle) but the cobalt
provides higher heat resistance allowing higher RPM and faster
drilling, which may be important in a production environment.

Since I'm in a cranky mood, this may be a good time to clarify something for
the newbies, who we may be confusing with some terminology.

What you're saying about these materials is correct, but "cobalt" is
misleading. There are many middle grades of HSS that contain some cobalt,
maybe 4% - 5%, such as M4 and M30. These are often called "cobalt high-speed
steel." And then there are the "high-cobalt" grades, often called "super
high-speed steel," or "cobalt super high-speed steel," or just "high-cobalt
high-speed steel." An example of a grade you'll find in quality tools is
M42. There also are more exotic grades used in industry.

But even M42 contains only around 8% cobalt. These are ALL just high-speed
steels, with more or less cobalt. There is no such thing as an all-cobalt
cutting tool, or even one with a lot of cobalt in it. There used to be some
very high-cobalt superalloy grades used in cutting, but they've long since
been replaced by carbides.

If you're buying from a clueless supplier, or one who thinks we're clueless
(like Sears), their "cobalt" tools might be M4 or something like it (if
you're lucky). If you buy good brand-name tools from a mill supply, they're
probably talking about M42. There's a big difference.

There. I feel better now. d8-)

--
Ed Huntress

On Jan 4, 1:43*pm, "Ed Huntress" wrote:
"F. George McDuffee" wrote in messagenews:7qs1m4pc3ia7kbp9jt0p3q1lvocs0k23g3@4ax .com...



On Sun, 4 Jan 2009 08:38:33 -0800 (PST), Ernst
wrote:

Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. *Not much
difference. *Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst
-------------
There are cobalt bits and there are cobalt bits. *From personal
experience and the many postings in these news groups it is
apparent that "Craftsman" quality has slipped in the past few
years. *You may want to try some name brand cobalt drills from a
mill supply.

Another consideration is that the cobalt bits are not necessarily
"harder" than HSS (although they are more brittle) but the cobalt
provides higher heat resistance allowing higher RPM and faster
drilling, which may be important in a production environment.

Since I'm in a cranky mood, this may be a good time to clarify something for
the newbies, who we may be confusing with some terminology.

What you're saying about these materials is correct, but "cobalt" is
misleading. There are many middle grades of HSS that contain some cobalt,
maybe 4% - 5%, such as M4 and M30. These are often called "cobalt high-speed
steel." And then there are the "high-cobalt" grades, often called "super
high-speed steel," or "cobalt super high-speed steel," or just "high-cobalt
high-speed steel." An example of a grade you'll find in quality tools is
M42. There also are more exotic grades used in industry.

But even M42 contains only around 8% cobalt. These are ALL just high-speed
steels, with more or less cobalt. There is no such thing as an all-cobalt
cutting tool, or even one with a lot of cobalt in it. There used to be some
very high-cobalt superalloy grades used in cutting, but they've long since
been replaced by carbides.

If you're buying from a clueless supplier, or one who thinks we're clueless
(like Sears), their "cobalt" tools might be M4 or something like it (if
you're lucky). If you buy good brand-name tools from a mill supply, they're
probably talking about M42. There's a big difference.

There. I feel better now. d8-)

--
Ed Huntress


Mmmm, I suspect that even with a super-duper cobalt HSS drill bit the
original poster is running it too fast for drilling a "hard bolt".

Supposing the bolt material is grade 8 or a socket head cap screw, the
bit should be running 40 t0 50 FPM cutting speed.

Or he is using just plain crappy drills which wouldn't do the job at
any speed.

Wolfgang

wrote in message
...
On Jan 4, 1:43 pm, "Ed Huntress" wrote:
"F. George McDuffee" wrote in
messagenews:7qs1m4pc3ia7kbp9jt0p3q1lvocs0k23g3@4ax .com...



On Sun, 4 Jan 2009 08:38:33 -0800 (PST), Ernst
wrote:

Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst
-------------
There are cobalt bits and there are cobalt bits. From personal
experience and the many postings in these news groups it is
apparent that "Craftsman" quality has slipped in the past few
years. You may want to try some name brand cobalt drills from a
mill supply.

Another consideration is that the cobalt bits are not necessarily
"harder" than HSS (although they are more brittle) but the cobalt
provides higher heat resistance allowing higher RPM and faster
drilling, which may be important in a production environment.

Since I'm in a cranky mood, this may be a good time to clarify something
for
the newbies, who we may be confusing with some terminology.

What you're saying about these materials is correct, but "cobalt" is
misleading. There are many middle grades of HSS that contain some cobalt,
maybe 4% - 5%, such as M4 and M30. These are often called "cobalt
high-speed
steel." And then there are the "high-cobalt" grades, often called "super
high-speed steel," or "cobalt super high-speed steel," or just
"high-cobalt
high-speed steel." An example of a grade you'll find in quality tools is
M42. There also are more exotic grades used in industry.

But even M42 contains only around 8% cobalt. These are ALL just high-speed
steels, with more or less cobalt. There is no such thing as an all-cobalt
cutting tool, or even one with a lot of cobalt in it. There used to be
some
very high-cobalt superalloy grades used in cutting, but they've long since
been replaced by carbides.

If you're buying from a clueless supplier, or one who thinks we're
clueless
(like Sears), their "cobalt" tools might be M4 or something like it (if
you're lucky). If you buy good brand-name tools from a mill supply,
they're
probably talking about M42. There's a big difference.

There. I feel better now. d8-)

--
Ed Huntress


Mmmm, I suspect that even with a super-duper cobalt HSS drill bit the
original poster is running it too fast for drilling a "hard bolt".

Supposing the bolt material is grade 8 or a socket head cap screw, the
bit should be running 40 t0 50 FPM cutting speed.

Or he is using just plain crappy drills which wouldn't do the job at
any speed.

Wolfgang

Or he's using the wrong machine to drive them. If it's a drill press, you
need some technique to drill hard steels. If it's a hand-held drill motor,
good luck. I'll watch.

--
Ed Huntress

Since I'm in a cranky mood, this may be a good time to clarify something for
the newbies, who we may be confusing with some terminology.

That the best you can do for a cranky mood? You need to try harder.

FWIW, I just made a wrong turn heading for my favorite shrimp shack
and went down the causeway to KCB. your old home town.

Karl

On Jan 4, 2:10*pm, "Ed Huntress" wrote:

Or he's using the wrong machine to drive them. If it's a drill press, you
need some technique to drill hard steels. If it's a hand-held drill motor,
good luck. I'll watch.


Thanks for the response(s). I suspected that cobalt bits came in
different flavors. Three things to help clarify the situation:

1. I'm basing comparative performance on experience in a
manufacturing environment. Once had to remove a fastener made of very
hard material (set screw as I recall). Went through several HSS bits
and barely made a divet. One of the other techs provided me with a
cobalt bit that went through the piece like butter.

2. I am using a hand held drill motor, variable speed, and have tried
several rates from slow to max.

3. These fasteners are used to hold storm shutters onto window
frames, have been in place for a while, and are apparently made of
nuclear-grade steel. I can't imagine why such a hard fastener was
used in the 1st place; I've had less trouble removing a broken head
bolt from a 302 with the engine in the car......

Lopping off the heads with a Dremel leaves the remainder of the screw
in place (obviously) which pins the screen frame to the window frame.
Trades one problem for another.

I have nine shutters to go.

Ernst

On Sun, 4 Jan 2009 12:33:50 -0800 (PST), Ernst
wrote:
snip
3. These fasteners are used to hold storm shutters onto window
frames, have been in place for a while, and are apparently made of
nuclear-grade steel. I can't imagine why such a hard fastener was
used in the 1st place;
snip
Most likely some sort of self-threading/tapping screw.

A useful trick that sometimes works is to get an old heavy
plumber's soldering iron, the type that you heat with a blow
torch, get it really hot, apply to the center of the screw head,
get the screw really hot, [tends to break the corrosion seal
between the aluminum frame and steel screw as the aluminum
expands more than the steel does] and unscrew ASAP. You can also
try penetrating oil, but I have never had much luck with this.
Anyone have a "secret formula" or brand for aluminum/steel
corrosion?


Unka' George [George McDuffee]
-------------------------------------------
He that will not apply new remedies,
must expect new evils:
for Time is the greatest innovator: and
if Time, of course, alter things to the worse,
and wisdom and counsel shall not alter them to the better,
what shall be the end?

Francis Bacon (1561-1626), English philosopher, essayist, statesman.
Essays, "Of Innovations" (1597-1625).

Those hard and tough fasteners are very hard to drill through. It
seems as though the drill gets much hotter drilling through that, than
through regular steel. (not surprising, since higher tenslie strength
means higher energy required to tear off those chips from parent
metal).

For anything very tough, I use carbide center cutting endmills or
carbide (solid or tipped) drills, my mill.

There is also a whole another level of drill bits called "harbor
freight $9.99 set". Those, not only fail drilling through mild steel,
but they also manage to leave some hard layer on it after they fail.

Do not forget lubrication.

--
Due to extreme spam originating from Google Groups, and their inattention
to spammers, I and many others block all articles originating
from Google Groups. If you want your postings to be seen by
more readers you will need to find a different means of
posting on Usenet.
http://improve-usenet.org/

On Sun, 4 Jan 2009 08:38:33 -0800 (PST), Ernst
wrote:

Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst


Colbalt are tougher, and stay sharper longer, and while a SIGNIFICANT
improvement over high speed steel IN THE PROPER APPLICATION....

they arent miracle workers.

Carbide, on the other hand.....those do work miracles if used properly.
If not, they become nightmares ........

"very hard" indicates to me...carbide.drills are required.


Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary
that Roosevelt would be remembered as a great president, "maybe even
alongside Washington and Lincoln," opining that Roosevelt "had every
quality that morons esteem in their heroes.""

Also, I've come across some plain ol' not-very-good HSS bits that were
gold-colored to resemble cobalt bits.

On Jan 4, 2:56*pm, F. George McDuffee gmcduf...@mcduffee-
associates.us wrote:

clip
Most likely some sort of self-threading/tapping screw. *

You are right, sir.

A useful trick that sometimes works is to get an old heavy
plumber's soldering iron, the type that you heat with a blow
torch, get it really hot, apply to the center of the screw head,
get the screw really hot, [tends to break the corrosion seal
between the aluminum frame and steel screw as the aluminum
expands more than the steel does] and unscrew ASAP. *You can also
try penetrating oil, but I have never had much luck with this.
Anyone have a "secret formula" or brand for aluminum/steel
corrosion?

Just the sight of the screws begged for saturation with Aero Kroil
(which happened). Wonder if application of a 100W Weller soldering
gun would work vice the plumber's iron?

Ernst

In article ,
Gunner Asch wrote:

On Sun, 4 Jan 2009 08:38:33 -0800 (PST), Ernst
wrote:

Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst


Colbalt are tougher, and stay sharper longer, and while a SIGNIFICANT
improvement over high speed steel IN THE PROPER APPLICATION....

they arent miracle workers.

Carbide, on the other hand.....those do work miracles if used properly.
If not, they become nightmares ........

"very hard" indicates to me...carbide.drills are required.

I've had good luck using cheap masonry drills for drilling out hardened
steel fasteners. Flood cooling does seem to help. I've always used a
drill press or mill, but I suppose freehand could work on smaller
fasteners.

Joe Gwinn

On Jan 4, 3:39*pm, Gunner Asch wrote:

Carbide, on the other hand.....those do work miracles if used properly.
If not, they become nightmares ........

What would be the best approach when using carbide bits with a hand
drill motor? One other thing: Ever used a diamond-coated bit? A
long, long time ago when I was a Navy jet mech, we had to drill out
some super-hard fasteners on an N1 case. If memory serves, someone
went to dental and got some "diamond dental bits". Whatever they
were, they worked pretty well.

Ernst

On Jan 4, 5:49*pm, Ernst wrote:
On Jan 4, 3:39*pm, Gunner Asch wrote:

Carbide, on the other hand.....those do work miracles if used properly.
If not, they become nightmares ........

What would be the best approach when using carbide bits with a hand
drill motor? *One other thing: *Ever used a diamond-coated bit? *A
long, long time ago when I was a Navy jet mech, we had to drill out
some super-hard fasteners on an N1 case. *If memory serves, someone
went to dental and got some "diamond dental bits". *Whatever they
were, they worked pretty well.

Ernst


Ernst,

What you describe is a horse of a different colour. Self-drilling &
tapping sheet metal screws are case hardened with the case hardness
approaching Rc70!

Tungsten carbide drill bits applied carefully are required to deal
with these. Unfortunately in a hand-held drill these drill bits often
break due to side-ways bending. With care though it should work, and
the higher speeds available would be a benefit.

Small T-G drills and endmills are available in Canada at Princess Auto
at very reasonable prices. They have a website catalogue but may not
list irregular surplus tools and equipment.

Wolfgang

Ernst wrote:
On Jan 4, 3:39 pm, Gunner Asch wrote:

Carbide, on the other hand.....those do work miracles if used
properly. If not, they become nightmares ........

What would be the best approach when using carbide bits with a hand
drill motor? One other thing: Ever used a diamond-coated bit? A
long, long time ago when I was a Navy jet mech, we had to drill out
some super-hard fasteners on an N1 case. If memory serves, someone
went to dental and got some "diamond dental bits". Whatever they
were, they worked pretty well.


FWIW:
I have used diamond coated bits in my Dremel to drill stones. I had bits
from two sources: One from Calgary which were awful and one from Hong Kong
which were fine. I built a baffle of plasticine around the prospective hole
and poured water in it and drilled the hole underwater with some success.

I tried the same thing only once with steel: Removal of a broken 6-32 tap.
Success was limited...

--
Michael Koblic,
Campbell River, BC

Since diamond would vaporize or dissolve into the metal it would be
best to use another super hard stone that wasn't pure carbon.

MSCdirect sells carbide drills. I used one to drill a hole into a
High speed steel 1/4" square metal turning steel. Normally one would
grind a shape and then cut steel with it. I drilled a hole and ground
off the front - now a U and a form tool.

It was red hot and cut through nicely.

Martin

Michael Koblic wrote:
Ernst wrote:
On Jan 4, 3:39 pm, Gunner Asch wrote:

Carbide, on the other hand.....those do work miracles if used
properly. If not, they become nightmares ........
What would be the best approach when using carbide bits with a hand
drill motor? One other thing: Ever used a diamond-coated bit? A
long, long time ago when I was a Navy jet mech, we had to drill out
some super-hard fasteners on an N1 case. If memory serves, someone
went to dental and got some "diamond dental bits". Whatever they
were, they worked pretty well.


FWIW:
I have used diamond coated bits in my Dremel to drill stones. I had bits
from two sources: One from Calgary which were awful and one from Hong Kong
which were fine. I built a baffle of plasticine around the prospective hole
and poured water in it and drilled the hole underwater with some success.

I tried the same thing only once with steel: Removal of a broken 6-32 tap.
Success was limited...

On 2009-01-04, Ernst wrote:
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Craftsman? Are you *sure* that they were real Cobalt steel? Go
for Cleveland or one of the other serious US drill bit makers, not
Craftsman, which could be imports from anywhere -- pseudo cobalt steel.
Judge Craftsman by the difference between Sears advertised horsepower on
a shop-vac or an air compressor, and the *real* horsepower determined by
objective measurements.

Second -- can you measure the hardness of what you were trying
to drill? Fastener heads -- *good* ones are quite hard, especially the
black-oxide finished ones, and probably would burn out most bits other
than perhaps solid carbide in a rigid enough machine. (Don't even *try*
solid carbide in a hand-held drill motor. :-)

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 ---

"DoN. Nichols" wrote in message
...
On 2009-01-04, Ernst wrote:
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Craftsman? Are you *sure* that they were real Cobalt steel? Go
for Cleveland or one of the other serious US drill bit makers, not
Craftsman, which could be imports from anywhere -- pseudo cobalt steel.
Judge Craftsman by the difference between Sears advertised horsepower on
a shop-vac or an air compressor, and the *real* horsepower determined by
objective measurements.

Second -- can you measure the hardness of what you were trying
to drill? Fastener heads -- *good* ones are quite hard, especially the
black-oxide finished ones, and probably would burn out most bits other
than perhaps solid carbide in a rigid enough machine. (Don't even *try*
solid carbide in a hand-held drill motor. :-)

Good Luck,
DoN.


I have also read about but not seen Stellite drill bits - apparently these
can operate red hot - maybe even orange hot, and so you just push hard and
let them melt their way through the hardened whatever you are trying to
drill.

for the particular application, left hand bits might be helpful because
there is a small chance they can start to loosen the fasteners.

note also, anti-seize may help reduce the problem the next time

On Sun, 4 Jan 2009 14:49:51 -0800 (PST), Ernst
wrote:

On Jan 4, 3:39*pm, Gunner Asch wrote:

Carbide, on the other hand.....those do work miracles if used properly.
If not, they become nightmares ........

What would be the best approach when using carbide bits with a hand
drill motor? One other thing: Ever used a diamond-coated bit? A
long, long time ago when I was a Navy jet mech, we had to drill out
some super-hard fasteners on an N1 case. If memory serves, someone
went to dental and got some "diamond dental bits". Whatever they
were, they worked pretty well.

Ernst


Carbide in a hand drill tends to get you a lot of busted drill bits.
They dont take sideways bending, something very hard not to do when
runnng a hand drill.

I can, after years of practice, not bust 1/8 and up, if Im very very
careful. But I generally stick carbide in a drill press.

Gunner

"Upon Roosevelt's death in 1945, H. L. Mencken predicted in his diary
that Roosevelt would be remembered as a great president, "maybe even
alongside Washington and Lincoln," opining that Roosevelt "had every
quality that morons esteem in their heroes.""

"Bill Noble" wrote in message
...

"DoN. Nichols" wrote in message
...
On 2009-01-04, Ernst wrote:
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Craftsman? Are you *sure* that they were real Cobalt steel? Go
for Cleveland or one of the other serious US drill bit makers, not
Craftsman, which could be imports from anywhere -- pseudo cobalt steel.
Judge Craftsman by the difference between Sears advertised horsepower on
a shop-vac or an air compressor, and the *real* horsepower determined by
objective measurements.

Second -- can you measure the hardness of what you were trying
to drill? Fastener heads -- *good* ones are quite hard, especially the
black-oxide finished ones, and probably would burn out most bits other
than perhaps solid carbide in a rigid enough machine. (Don't even *try*
solid carbide in a hand-held drill motor. :-)

Good Luck,
DoN.


I have also read about but not seen Stellite drill bits - apparently these
can operate red hot - maybe even orange hot, and so you just push hard and
let them melt their way through the hardened whatever you are trying to
drill.

They're pretty much obsolete. They combine the hardness of low-grade HSS
with less thermal tolerance than carbide, and with most of the brittleness
of carbide. Micrograin carbides are better in almost every way, especially
when you aren't using them in modern, rigid machine tools. For use in modern
machine tools, other carbides may be better. For use in hand-held drill
motors...I'll still stand back and watch. g


for the particular application, left hand bits might be helpful because
there is a small chance they can start to loosen the fasteners.

note also, anti-seize may help reduce the problem the next time

"Ernst" wrote in message
...
snip--
1. I'm basing comparative performance on experience in a
manufacturing environment. Once had to remove a fastener made of very
hard material (set screw as I recall). Went through several HSS bits
and barely made a divet. One of the other techs provided me with a
cobalt bit that went through the piece like butter.

By hand? I'd be surprised if that was the case. What cobalt offers is
hardness at elevated temperatures. In the case of the set screw, money
says that you heated the screw to the point of hardness collapse. It
doesn't take much if it is hardened by the carbon cycle.

2. I am using a hand held drill motor, variable speed, and have tried
several rates from slow to max.

You've already been wished good fortune. I'm going to suggest that it
probably won't happen. Cobalt drills have a much heavier web than plain HSS
drills, so the pressure required to drill is much greater. I doubt you can
keep the needed pressure on the hardened piece long enough to raise the
temperature to the point where it will drill well. Any chance you can
tip the building on its side and get it under a spindle with a lever feed?
g

Harold

3. These fasteners are used to hold storm shutters onto window
frames, have been in place for a while, and are apparently made of
nuclear-grade steel. I can't imagine why such a hard fastener was
used in the 1st place; I've had less trouble removing a broken head
bolt from a 302 with the engine in the car......

Lopping off the heads with a Dremel leaves the remainder of the screw
in place (obviously) which pins the screen frame to the window frame.
Trades one problem for another.

I have nine shutters to go.

Ernst

On 2009-01-05, Bill Noble wrote:

"DoN. Nichols" wrote in message
...

[ ... ]

Craftsman? Are you *sure* that they were real Cobalt steel? Go
for Cleveland or one of the other serious US drill bit makers, not

[ ... ]

I have also read about but not seen Stellite drill bits - apparently these
can operate red hot - maybe even orange hot, and so you just push hard and
let them melt their way through the hardened whatever you are trying to
drill.

Hmm ... I've never heard about *drill* bits made of Stellite,
but I have a couple of *lathe* bits (thanks to Harold Vrodos, from whom
I learned about them.

Making drill bits from that is probably as difficult as making
them from solid carbide -- but they would be nice to have.

for the particular application, left hand bits might be helpful because
there is a small chance they can start to loosen the fasteners.

Agreed -- but only if the shank of the screw is large enough so
a reasonable strength drill bit could be used.

note also, anti-seize may help reduce the problem the next time

Next time! Too late now. (And he probably did not have any
control over how they were originally installed. :-)

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 ---

On Jan 6, 2:30*am, "Harold and Susan Vordos" wrote:

You've already been wished good fortune. *I'm going to suggest that it
probably won't happen. *Cobalt drills have a much heavier web than plain HSS
drills, so the pressure required to drill is much greater. * I doubt you can
keep the needed pressure on the hardened piece long enough to raise the
temperature to the point where it will drill well. * *

Begs some questions: What is the proper technique? Lube? no lube?
high speed or low?

Any chance you can
tip the building on its side and get it under a spindle with a lever feed?
g

Well, I had considered sinking bolts into the structure in order to
mount a rectangular steel framework, to provide support for a chainsaw-
motor-powered drill head.... ;-)

Ernst

On Jan 5, 12:27*am, "DoN. Nichols" wrote:

* * * * Craftsman? *Are you *sure* that they were real Cobalt steel? *Go
for Cleveland or one of the other serious US drill bit makers, not
Craftsman, which could be imports from anywhere -- pseudo cobalt steel.

Haven't done any chemical, spectrometric, or rockwell analysis on the
bits, so the short answer would be "no, I'm not sure". Package says
"Cobalt" although there are no MIL-SPECs or other grading standards
listed. From what I gather above, cobalt is by degree, so I suspect
these are on the fringe.

Seems they are inappropriate for the task anyway. I'm going to try
the bits with a grade-8 fastener and see how they fare.

* * * * Second -- can you measure the hardness of what you were trying
to drill? *Fastener heads -- *good* ones are quite hard, especially the
black-oxide finished ones, and probably would burn out most bits other
than perhaps solid carbide in a rigid enough machine. (Don't even *try*
solid carbide in a hand-held drill motor. :-)

* * * * Good Luck,
* * * * * * * * DoN.

Thanks. I'm going to use valve-lapping compound on the screwdriver
for more bite and hopefully avoid too many more screws that require
special attention. The Dremel is the silver bullet this time.

Ernst

"Ernst" wrote in message
...

Begs some questions: What is the proper technique? Lube? no lube?
high speed or low?

My limited experience when altering some existing defense parts was to run
(reasonably) fast, with no lube. Bear down, then when it's hot enough, the
drill starts cutting. Heat, on heat treated parts, is very much part of the
reason these drills work. They tend to anneal the hard material at the
point of contact. The cobalt content allows them to retain the necessary
hardness at elevated temperatures.

Harold

Maybe an easier approach would be cutting away the broken off screws, Ernst.

There are some small hole saws for use in drills or die grinders with 1/4"
collets that could be used to cut out the base metal around the frozen
screw.
I saw some yesterday that had diamond grit on them, but carbon steel saw
teeth or carbide grit would likely be better.

Another method would be to use a piece of tubing in a drill chuck and dip it
in a grit paste like valve grinding compound. May get a bit messy, but a
good solvent on a rag should be all that's required for cleanup, just avoid
too much rubbing.

I think you mentioned the screws were in a window frame of some sort. If
there is a feature (channel or edge) that would position a guide over the
screw stub (so the hole saw can't run away), make up a guide for a small
hole saw that could be clamped into position for cutting out a broken screw,
then repositioned over another, etc.

It shouldn't be too difficult to find something to fill the hole (push-in
plastic gizzy, etc) for a new screw to anchor in.. or just fill the holes
with some "miracle hole filler in a tube" and screw into that.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Ernst" wrote in message
...
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst

On Fri, 9 Jan 2009 21:44:37 -0500, "Wild_Bill"
wrote:

Maybe an easier approach would be cutting away the broken off screws, Ernst.

There are some small hole saws for use in drills or die grinders with 1/4"
collets that could be used to cut out the base metal around the frozen
screw.
I saw some yesterday that had diamond grit on them, but carbon steel saw
teeth or carbide grit would likely be better.

Another method would be to use a piece of tubing in a drill chuck and dip it
in a grit paste like valve grinding compound. May get a bit messy, but a
good solvent on a rag should be all that's required for cleanup, just avoid
too much rubbing.

I think you mentioned the screws were in a window frame of some sort. If
there is a feature (channel or edge) that would position a guide over the
screw stub (so the hole saw can't run away), make up a guide for a small
hole saw that could be clamped into position for cutting out a broken screw,
then repositioned over another, etc.

It shouldn't be too difficult to find something to fill the hole (push-in
plastic gizzy, etc) for a new screw to anchor in.. or just fill the holes
with some "miracle hole filler in a tube" and screw into that.
When I had a screw in the corner of a shower door panel with the head
broken off, I was able to go through the slot in the extrusion with a
Dremel cut off wheel and cut a slot through the axis of the remainder
of the screw whereupon the two slivers of screw were easily persuaded
to fall out.
Gerry :-)}
London, Canada

Yep, a Dremel tool or similar rotary tool can save a lot of grief sometimes.
A very valuable tool when they are needed.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


"Gerald Miller" wrote in message
...
When I had a screw in the corner of a shower door panel with the head
broken off, I was able to go through the slot in the extrusion with a
Dremel cut off wheel and cut a slot through the axis of the remainder
of the screw whereupon the two slivers of screw were easily persuaded
to fall out.
Gerry :-)}
London, Canada

In article cab8b2a4-f141-4405-874a-db516a17195a@
20g2000yqt.googlegroups.com, says...
Hello All,

I had the occassion to drill through some very hard fasteners.
Standard HSS bits were becoming dull in a very short timespan, so I
opted for cobalt bits to continue.

Armed with a set of Craftsman bits, I went back to work. Not much
difference. Altering speeds, using light oil, nothing really worked.
Ended up using a Dremel tool with a cut-off disc to remove the
fastener heads (which presents other problems).

What gives?

Regards,

Ernst

Coblat isn't that much harder than HSS, they just have better high
temperature hardness. You might try repointing a masonery bit. Not
guaranteed, but it's a lot cheaper than full blown carbide drills.