Homebrew PCBs

Hi,

I went thru the list and found some comments on bits for etching.

It seems like the box of 50 burrs from Harbor Freight are the best 
bang for the buck, IF they last.

has anybody used them ?

any reports on how well they last ?

Dave

In a message dated 1/12/2003 12:39:07 PM Central Standard Time, 
dave_mucha@... writes:


> It seems like the box of 50 burrs from Harbor Freight are the best bang for 
> the buck, IF they last.
> 

Dave:  You didn't mention if these are solid-carbide, diamond-"plated", or 
what.  Carbide holds up well against such as FR-4 ("glass-epoxy"),  Diamond 
would "forever", if the diamond were the ONLY material touching the 
glass-fibers, but that "diamond plated" stuff is just that:  They 
nickel-plate diamond-grit onto a HSS spindle, so as soon as the nickel 
outer-"skin" is worn off (within first two seconds of use!), there is little 
"holding" the diamond bits on the steel.  AND, there is plenty of steel 
(nickel-plated or not!) exposed to the glass-fibers, between the rather OPEN 
grit-area, at the start!  

I found out LONG ago that even the "new wholesale" price of solid-carbide 
drill-bits (often more than $2.00 per bit!) is cheaper "per hole successfully 
drilled" than ANY HSS drill-bits, even if you can resharpen them yourself 
(every twenty holes?), and have a "chuck" capable of gripping HSS bits, which 
are NOT made with "One Size Fits All" 1/8" dia. shanks as are carbide bits.  

A carefully-zealous "browsing shopper" can find BOXES of useful-sizes of 
solid-carbide bits offered in the various mail-order catalogs such as JDR 
Microdevices and JAMECo, etc.  I don't know that their current pricing is 
like, but I have bought several boxes of 50 "reconditioned" bits of size #57 
or #65, etc., for less than $1.00 per bit!  NEVER throw away the 1/8" shank 
when the "drill-part" breaks off, as that is VERY useful "tool-making stuff"! 
 All you need is a little diamond-wheel on a little grinder-motor, some 
imagination, and minimal skill!

I do not "machine-etch" PCB's (easier to chemically-etch!!!), but I note 
there are many "of us" who do, and I wonder why no one has offered that these 
busted, "useless" (NOT!) solid-carbide drill-shanks would be ideal for the 
tooling on a machine-etching job!  Ya just have to grind an "engraver's tip" 
on the pointed-end of the shank (where the drill-part left for a galaxy far, 
far away)!   True, one must have a nice small lathe (Unimat, Sherline, Taig, 
etc.), if not a "bit holding fixture" and a diamond-cup-wheel grinder rig, 
and some wisdom and skill.   Some may-well know a "machinist-friend" who 
grinds his own tooling, who will do these as a favor.  Might be a "project" 
for some ambitious soul!  Others might find some grinding-shop willing to DO 
this "for us all" at a reasonable price, mail-order---we just supply the 
shanks/blanks.  Can someone with more wisdom on this point comment???

Jan Rowland, old troll








[Non-text portions of this message have been removed]

Hi Jan,

yes, the box of 50 solid carbid, 'reconditioned' bits in various 
sizes.

My Old Scott nameplate engraver uses a half flute single edge for 
cutting and for milling, that seems like the simplest way.  and you 
can do that by hand if you have a diamond wheel.

The mechanics about what you pointed out is that the fiberglass does 
not creat chips and leave the cutting zone, it powders and eats away 
at soft stuff in the area.  I have had to drill cindeblock on 
occasion and used standard HSS drills.  probably lasted about as long 
as HSS in PC boards.

With my limtied metal working experiance, I have firmly come to the 
conclusion that you 'can' do the impossible, but it takes time and 
effort.  you 'can' regrind after every few holes or just buy the 
correct bits in the firstplace.

I too have a box full of punches and scribes made of broken tooling.  
can't beat good carbide for putting your mark on parts.

I was wondering how well these reconditioned bits work ? why they are 
sooo cheap ?  are they undersized ?  bad units? factory rejects?  how 
can so many people sell them ? maybe it is a PCB factory waste 
product from the far east.  Sombody has to make all the PCBs  for our 
TV's and Radio's.

Dave




--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 1/12/2003 12:39:07 PM Central Standard Time, 
> dave_mucha@y... writes:
> 
> 
> > It seems like the box of 50 burrs from Harbor Freight are the 
best bang for 
> > the buck, IF they last.
> > 
> 
> Dave:  You didn't mention if these are solid-carbide, diamond-
"plated", or 
> what.  Carbide holds up well against such as FR-4 ("glass-epoxy"),  
Diamond 
> would "forever", if the diamond were the ONLY material touching the 
> glass-fibers, but that "diamond plated" stuff is just that:  They 
> nickel-plate diamond-grit onto a HSS spindle, so as soon as the 
nickel 
> outer-"skin" is worn off (within first two seconds of use!), there 
is little 
> "holding" the diamond bits on the steel.  AND, there is plenty of 
steel 
> (nickel-plated or not!) exposed to the glass-fibers, between the 
rather OPEN 
> grit-area, at the start!  
> 
> I found out LONG ago that even the "new wholesale" price of solid-
carbide 
> drill-bits (often more than $2.00 per bit!) is cheaper "per hole 
successfully 
> drilled" than ANY HSS drill-bits, even if you can resharpen them 
yourself 
> (every twenty holes?), and have a "chuck" capable of gripping HSS 
bits, which 
> are NOT made with "One Size Fits All" 1/8" dia. shanks as are 
carbide bits.  
> 
> A carefully-zealous "browsing shopper" can find BOXES of useful-
sizes of 
> solid-carbide bits offered in the various mail-order catalogs such 
as JDR 
> Microdevices and JAMECo, etc.  I don't know that their current 
pricing is 
> like, but I have bought several boxes of 50 "reconditioned" bits of 
size #57 
> or #65, etc., for less than $1.00 per bit!  NEVER throw away the 
1/8" shank 
> when the "drill-part" breaks off, as that is VERY useful "tool-
making stuff"! 
>  All you need is a little diamond-wheel on a little grinder-motor, 
some 
> imagination, and minimal skill!
> 
> I do not "machine-etch" PCB's (easier to chemically-etch!!!), but I 
note 
> there are many "of us" who do, and I wonder why no one has offered 
that these 
> busted, "useless" (NOT!) solid-carbide drill-shanks would be ideal 
for the 
> tooling on a machine-etching job!  Ya just have to grind 
an "engraver's tip" 
> on the pointed-end of the shank (where the drill-part left for a 
galaxy far, 
> far away)!   True, one must have a nice small lathe (Unimat, 
Sherline, Taig, 
> etc.), if not a "bit holding fixture" and a diamond-cup-wheel 
grinder rig, 
> and some wisdom and skill.   Some may-well know a "machinist-
friend" who 
> grinds his own tooling, who will do these as a favor.  Might be 
a "project" 
> for some ambitious soul!  Others might find some grinding-shop 
willing to DO 
> this "for us all" at a reasonable price, mail-order---we just 
supply the 
> shanks/blanks.  Can someone with more wisdom on this point 
comment???

> 
> Jan Rowland, old troll
> 
> 
> 
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]

In a message dated 1/12/2003 5:04:39 PM Central Standard Time, 
dave_mucha@... writes:


> I was wondering how well these reconditioned bits work ? why they are sooo 
> cheap ?  are they undersized ?  bad units? factory rejects?  how can so 
> many people sell them ? maybe it is a PCB factory waste product from the 
> far east.  Sombody has to make all the PCBs  for our TV's and Radio's.

Dave:  GOOD questions, and ones I think worthy of discussion "here"!  I have 
wondered this myself, and I have had to rely only on my "imagination" for 
answers, as it is not SO earth-shaking a quest that'd I'd "get in the car and 
drive about to the several PC-houses within 50 miles, to inquire"!  

They work very well on MY "CNC" drill, so long as the machine makes NO 
attempt to "move to next hole" before the quill is 100% UP and still.  And, 
for hundreds of holes, it seems, before dull.  Actually, I have never 
"dulled" a carbide bit, yet!  I have also used them in a vertical mill (used 
as "drill-press") to drill HSS with success.  Carbide is AMAZINGLY tough 
stuff!  

The word "recoditioned" merely means "re-sharpened"!  I do NOT think they are 
"bad", "rejects", or "far east waste".  I think they are simply "sold cheap" 
to those who scarf-up such, and re-sharpened, as the PCB-houses probably 
drill almost-ONLY in "stacks", so that re-sharpened bits would be just TOO 
short to be useful for that application.  MY guess.  

Yes, I am GUESSING that the houses that drill those PCB's for "our TV's and 
computers" go through MILLIONS of these bits (ever see a PCB machine drill, 
and CHANGE ITS OWN BITS?  Wizardry!  Four or five holes per second, through 
four STACKS up to 7 boards deep!  100,000 and up RPM air-drills!  So, 
mind-bending as it is, I guess there ARE sources for those "boxes of fifty" I 
have seen offered by, oh, three or four mail-order houses.  Yes.  Whew!

Surely there is SOMEone "in here" who is "professional" or has a sister who's 
husband's cousin works for a PCB-house who can TELL us how far-off I am with 
these guesses???  We'd ALL like to know?

Jan Rowland


[Non-text portions of this message have been removed]

We have a PCB layout guy here at work that worked most of his life at a PCB
house before working for us. He says that all those 'reconditioned' bits are
because the PCB industry needs such incredibly tight tolerances in hole
width, that after a certain number of holes, the drills are out of 'spec'
and can't be used. They aren't that dull, they're just a bit too narrow for
precision use. They stop using bits if they are actually out of spec or not
- there's just a certain limit (number of holes I guess) and after that
limit, the bits are discarded. They can be cheaply re-sharpened and sold to
people like us, so throwing them out isn't all that expensive for the PCB
house as they get some money back for their investment. My friend said that
it's much more expensive (because of an increase in the amount of 'errors'
in a board) to use a bit that might be out of spec than to just use new bits
every x holes. I couldn't believe the tolerances he was talking about in the
higher end PCB shops. These guys really have their processes down.

*Brian

> Dave:  GOOD questions, and ones I think worthy of discussion 
> "here"!  I have 
> wondered this myself, and I have had to rely only on my 
> "imagination" for 
> answers, as it is not SO earth-shaking a quest that'd I'd 
> "get in the car and 
> drive about to the several PC-houses within 50 miles, to inquire"!

We always drilled a maximum depth of five times the drill diameter. 
This was the general rule of thumb for carbide bits. Most of the time 
we drilled a stack of panels three deep  and only one deep if they 
were multilayer boards. We sharpened our bits only two or three times 
and then sold them off. Most bits need to be resharpened after about 
2000 to 2500 hits. 

When drilling multilayers we always used new bits and never resharps. 
Our bits were used first for multilayers, resharpened and then used 
on two layer panels for a couple of cycles and then junked. Many 
shops now days are only doing multilayer work so they put out tons of 
bits that have drilled 2500 or less holes. These are the bits to get. 
For single sided and hobby boards you can just about drill until they 
break although the dull bits will make a larger burr.

The original auto tool changers were "pods" located along the front 
of the drill table. The idea was for the machine to dump the bit and 
then pick up the next one etc. They almost never worked correctly and 
many shops just put their machines in a manual tool change mode. Many 
newer machines have large capacity "cassette" type tool holders and 
these work pretty good, much better than the original pod type.
I found that the machines would break more bits by crashing them into 
the tool pods. The bits almost never break during drilling.

In the "manual" mode when a tool run was complete the machine table 
would move to the "home" position and stop. The spindles had a 
dynamic braking circuit to stop them in about four or five seconds. 
These spindle bearings were so good that a new spindle might spin for 
two minutes after the power was removed so the braking circuit was 
needed. 

The spindles were driven by a three phase frequency converter and the 
dynamic brake circuit put 7 volts DC across one of the windings to 
stop the spindle rotation. All of these spindles used .125" collets 
and the plastic ring on the bit was used to set the depth. These 
rings were pressed on so that the tip of the bit to the top of the 
ring was set for .81". The Z axis of the machine could then be set 
for a precise drill depth. Hope this info answers some of the bit 
questions.

Tom

twb8899 wrote:
> 
[deleted other interesting paragraphs]

> When drilling multilayers we always used new bits and never resharps. 
> Our bits were used first for multilayers, resharpened and then used 
> on two layer panels for a couple of cycles and then junked. Many 
> shops now days are only doing multilayer work so they put out tons of 
> bits that have drilled 2500 or less holes. These are the bits to get. 
> For single sided and hobby boards you can just about drill until they 
> break although the dull bits will make a larger burr.
> 

Thanks Tom for sharing your knowledge with the group, although I have couple of 
questions.

What is different about the holes drilled in multilayer boards that make it you 
cannot use re-sharpened bits ?  Is it because the bore is left smoother with a 
new drill bit and sometimes that makes a more reliable copper connection 
(electroless plated) to the inner layers ?

I read that they etch back the epoxy to make sure "drill smear" does not cover 
the exposed copper foil of inneralyers inside the holes. The process is called 
"desmear" and consists of three steps. An epoxy swell (a water miscible organic 
solvent), epoxy etch (hot potassium permaganate/hydroxide), followed by 
neutralize (sulfuric acid/ammonium persuflate). Is this what you used to do ?

I would imagine that after epoxy desmearing that it wont matter what mess is 
left behind after drilling with old & blunt bits.

Adam

In a message dated 1/15/2003 2:29:33 AM Central Standard Time, 
twb8899@... writes:


>  Hope this info answers some of the bit questions.


Wow!  Thanks, Tom!  That is VERY useful to us hobby-folk!

Yeah, I watched a 4-quill CNC PCB-drill with "pods" change its own bits, and 
all SEEMED to be fine, but I just could NOT help thinking, as I walked away, 
"This CAN'T be so reliable ALL the time?!!!"  GOOD to hear it isn't!

Interesting you say the quill motors are electric.  I was told they are 
PNEUMATIC, to run at 100,000 RPM!  Hmmm...

Jan Rowland





[Non-text portions of this message have been removed]

Adam,

Everything you mentioned about etch back and desmearing is correct. 
In our process we used new drill bits for multilayers to mainly limit 
the amount of smearing. There could have been a requirement for this 
in the MIL-55110P specification as well. Some MIL requirements would 
require stuff like that. A new sharp bit helps big time on 
multilayers since you need a good sharp cut through the inner layer 
copper. These multilayer panels were so expensive that the bit cost 
was a small fraction of the overall cost. It just wasn't worth the 
risk drilling with used bits or resharps. The multilayer pre-preg 
bonding materials have improved over the years so it's probably not 
such a big deal any longer but we all know how hard it is to break 
old habits. 

When we went to the newer activated palladium catalyst in 1990 we no 
longer needed desmearing for commercial multilayers. We only did a 
slight etchback with straight technical grade (92.8%) sulfuric acid. 
Desmearing was still performed on military boards though because of 
the MIL specifications. 

Tom



--- In Homebrew_PCBs@yahoogroups.com, adam Seychell 
<adam_seychell@y...> wrote:
> 
> 
> twb8899 wrote:
> > 
> [deleted other interesting paragraphs]
> 
> > When drilling multilayers we always used new bits and never 
resharps. 
> > Our bits were used first for multilayers, resharpened and then 
used 
> > on two layer panels for a couple of cycles and then junked. Many 
> > shops now days are only doing multilayer work so they put out 
tons of 
> > bits that have drilled 2500 or less holes. These are the bits to 
get. 
> > For single sided and hobby boards you can just about drill until 
they 
> > break although the dull bits will make a larger burr.
> > 
> 
> Thanks Tom for sharing your knowledge with the group, although I 
have couple of 
> questions.
> 
> What is different about the holes drilled in multilayer boards that 
make it you 
> cannot use re-sharpened bits ?  Is it because the bore is left 
smoother with a 
> new drill bit and sometimes that makes a more reliable copper 
connection 
> (electroless plated) to the inner layers ?
> 
> I read that they etch back the epoxy to make sure "drill smear" 
does not cover 
> the exposed copper foil of inneralyers inside the holes. The 
process is called 
> "desmear" and consists of three steps. An epoxy swell (a water 
miscible organic 
> solvent), epoxy etch (hot potassium permaganate/hydroxide), 
followed by 
> neutralize (sulfuric acid/ammonium persuflate). Is this what you 
used to do ?
> 
> I would imagine that after epoxy desmearing that it wont matter 
what mess is 

> left behind after drilling with old & blunt bits.
> 
> Adam

Jan,

The big professional drilling machines all use electric spindles but 
some have air bearings for rotation. These air bearing spindles have 
no ball bearings and therefore no metal to metal contact. Everything 
spins on an air cushion with almost no run out. Very small holes can 
be drilled with this type of spindle. The spindles are electric 
driven to obtain the torque needed especially for larger holes. 

All of my machines had ball bearing spindles, however, the spindles 
did slide up and down in a cushion of air for very fast action. The 
XY table also rides on an air cushion against the granite table.
My favorite machine was an Excellon EX-200 Driller/Router. This was 
considered a "small"(6500 lbs!) machine. It had three spindles and 
could drill or route three stacks of panels up to 12" x 24". It also 
had an optical scope for digitizing. We used this machine for all of 
our engineering and prototype work. The original specifications said 
this machine could drill 400 holes per minute. This was probably true 
for a .1" grid drilling only one deep. Our average drilling rate was 
around 150 holes per minute when drilling three panels deep.

I shut off the auto tool changer mode since it just wasn't reliable 
(ask any Excellon service tech!). Several types of spindles were 
available but I used the 60,000 rpm drill/route spindles on the EX-
200 and 80,000 drill only spindles on the other machines. The air 
requirements for these machines was about 20 cfm at 90 psi. 

Tom


--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 1/15/2003 2:29:33 AM Central Standard Time, 
> twb8899@y... writes:
> 
> 
> >  Hope this info answers some of the bit questions.
> 
> 
> Wow!  Thanks, Tom!  That is VERY useful to us hobby-folk!
> 
> Yeah, I watched a 4-quill CNC PCB-drill with "pods" change its own 
bits, and 
> all SEEMED to be fine, but I just could NOT help thinking, as I 
walked away, 
> "This CAN'T be so reliable ALL the time?!!!"  GOOD to hear it isn't!
> 
> Interesting you say the quill motors are electric.  I was told they 
are 

> PNEUMATIC, to run at 100,000 RPM!  Hmmm...
> 
> Jan Rowland
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]

I am surprised at the air consumption and that they would use 
electric motors for drilling.  the motors would be much bigger than a 
similar power air motor.

Dave




--- In Homebrew_PCBs@yahoogroups.com, "twb8899 <twb8899@y...>" 
<twb8899@y...> wrote:
> Jan,
> 
> The big professional drilling machines all use electric spindles 
but 
> some have air bearings for rotation. These air bearing spindles 
have 
> no ball bearings and therefore no metal to metal contact. 
Everything 
> spins on an air cushion with almost no run out. Very small holes 
can 
> be drilled with this type of spindle. The spindles are electric 
> driven to obtain the torque needed especially for larger holes. 
> 
> All of my machines had ball bearing spindles, however, the spindles 
> did slide up and down in a cushion of air for very fast action. The 
> XY table also rides on an air cushion against the granite table.
> My favorite machine was an Excellon EX-200 Driller/Router. This was 
> considered a "small"(6500 lbs!) machine. It had three spindles and 
> could drill or route three stacks of panels up to 12" x 24". It 
also 
> had an optical scope for digitizing. We used this machine for all 
of 
> our engineering and prototype work. The original specifications 
said 
> this machine could drill 400 holes per minute. This was probably 
true 
> for a .1" grid drilling only one deep. Our average drilling rate 
was 
> around 150 holes per minute when drilling three panels deep.
> 
> I shut off the auto tool changer mode since it just wasn't reliable 
> (ask any Excellon service tech!). Several types of spindles were 
> available but I used the 60,000 rpm drill/route spindles on the EX-
> 200 and 80,000 drill only spindles on the other machines. The air 
> requirements for these machines was about 20 cfm at 90 psi. 
> 
> Tom
> 
> 
> --- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> > In a message dated 1/15/2003 2:29:33 AM Central Standard Time, 
> > twb8899@y... writes:
> > 
> > 
> > >  Hope this info answers some of the bit questions.
> > 
> > 
> > Wow!  Thanks, Tom!  That is VERY useful to us hobby-folk!
> > 
> > Yeah, I watched a 4-quill CNC PCB-drill with "pods" change its 
own 
> bits, and 
> > all SEEMED to be fine, but I just could NOT help thinking, as I 
> walked away, 
> > "This CAN'T be so reliable ALL the time?!!!"  GOOD to hear it 
isn't!
> > 
> > Interesting you say the quill motors are electric.  I was told 
they 

> are 
> > PNEUMATIC, to run at 100,000 RPM!  Hmmm...
> > 
> > Jan Rowland
> > 
> > 
> > 
> > 
> > 
> > [Non-text portions of this message have been removed]

In a message dated 1/18/2003 6:17:44 AM Central Standard Time, 
twb8899@... writes:


> Several types of spindles were available but I used the 60,000 rpm 
> drill/route spindles on the EX-200 and 80,000 drill only spindles on the 
> other machines. The air requirements for these machines was about 20 cfm at 
> 90 psi.

Tom:  

TWO points:  60,000 and 80,000 RPM?  Were these "high frequency" motors, or 
"brush motors"?  TEFC, I would assume!

WOW, 20 CFM at 90 PSI!  That would keep a 10 hp compressor running possibly 
over 50% duty-cycle!  Wouldn't it?

Jan Rowland


[Non-text portions of this message have been removed]

Dave and Jan,

Yes, these big machines took lots of air to run them. The air 
requirements are because of the air bearing table and spindle 
sleeves. Each axis glides on a cushion of air in these systems. 

Our air source was a 15 HP, 60 CFM rotary screw compressor. It would 
carry all three of our machines but it was a rare occasion when more 
than two machines were running at the same time. 

The spindle motors have high frequency three phase motors. There is a 
frequency converter in the machine that drives a high voltage 
transistor output stage at about 150 volts. The frequency is 
controlled by the CPU and displayed on the CRT screen as spindle 
speed. 

If you ever get the chance to watch one of these Excellon machines 
run you will certainly be amazed. Try to watch even one hole being 
drilled and ten more will be drilled before your eyes can focus on 
one... these machines really scream.

Tom


--- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> In a message dated 1/18/2003 6:17:44 AM Central Standard Time, 
> twb8899@y... writes:
> 
> 
> > Several types of spindles were available but I used the 60,000 
rpm 
> > drill/route spindles on the EX-200 and 80,000 drill only spindles 
on the 
> > other machines. The air requirements for these machines was about 
20 cfm at 
> > 90 psi.
> 
> Tom:  
> 
> TWO points:  60,000 and 80,000 RPM?  Were these "high frequency" 
motors, or 
> "brush motors"?  TEFC, I would assume!
> 
> WOW, 20 CFM at 90 PSI!  That would keep a 10 hp compressor running 
possibly 

> over 50% duty-cycle!  Wouldn't it?
> 
> Jan Rowland
> 
> 
> [Non-text portions of this message have been removed]

In a message dated 1/19/2003 4:29:47 PM Central Standard Time, 
twb8899@... writes:


> If you ever get the chance to watch one of these Excellon machines 
> run you will certainly be amazed. Try to watch even one hole being 
> drilled and ten more will be drilled before your eyes can focus on 
> one... these machines really scream.


Yes, Tom, I have SEEN a 4-quill drill stacks of 7-high blanks, and the "peck 
rate" was two to five holes per second (I am not an f-meter, myself, so I 
could not tell exactly how fast).  But I could have SWORN the quill-motors 
were air-driven.  Probably the operators had no clue, themselves!   
Definitely a mind-bending thing to watch!  $$$$!!!!!!!!!

High-F, huh?  Lessee, if 400 Hz. can make 24,000 RPM (woodworking machinery 
with which I had a tiny bit of hands-on), then 80,000 would require 1.33 kHz. 
"AC" 3-phase.  WOW!  Guess that's no big deal electronically, but the EMI 
must be SUMMIN to deal with!

Well, appreciate the info!             Jan Rowland


[Non-text portions of this message have been removed]

JanRwl@... wrote:
> In a message dated 1/18/2003 6:17:44 AM Central Standard Time, 
> twb8899@... writes:
> 
> 
> 
>>Several types of spindles were available but I used the 60,000 rpm 
>>drill/route spindles on the EX-200 and 80,000 drill only spindles on the 
>>other machines. The air requirements for these machines was about 20 cfm at 
>>90 psi.
> 
> 
> Tom:  
> 
> TWO points:  60,000 and 80,000 RPM?  Were these "high frequency" motors, or 
> "brush motors"?  TEFC, I would assume!
> 
> WOW, 20 CFM at 90 PSI!  That would keep a 10 hp compressor running possibly 
> over 50% duty-cycle!  Wouldn't it?
> 
> Jan Rowland
> 


I haven't seen these motors running my self, but I know they carry a 
hefty price tag (secondhand AUD$2500) and suck a lot of juice. I 
learned this when I was shopping around for a PCB spindle for my home 
made manual drilling machine. They need a variable frequency variable 
voltage 3 phase power supply (voltage is proportional to speed because 
of back EMF). I think the guy selling them said they run up to 250V at 
full RPM. They can use precision ball bearings under 100,000 RPM and 
air bearings for higher speeds. I did not buy one of course. Check the 
following link.

http://www.westwind-airbearings.com/

Adam