Homebrew PCBs

In this case it was the tool. The drill stand to be exact. I did not
really notice the slop when I was drilling larger holes with HSS bits.
I guess HSS is a little more forgiving, than carbide. There was no way
to adjust the slop out. I would not even think of hand drilling this.
I am way to clumsy.

So I bought a Cameron Micro Drill. I did not want to spend two months
worth of weekends trying to hack together a better tool. I want to
finish the current electonics project and push onto others. I just
finished drilling 23 #85 holes like a hot knife through butter and
without breaking a bit.

Could I have bought cheaper, yes. However I know the microdrill will
do the job, do it well and I can push on to other things.

It is a balance between money, time and skill. In this case I decided
in favor of money to move things along.



--- In Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
> javaguy11111 wrote:
> > I just got a set of resharpened carbide bits in from drill city. I
> > chuck one up into my dremel press. I snap the bit on the first
hole.
> > Thinking maybe I moved the board, I tried a second bit and
snapped it
> > as well. This was with a #81 bit. So I thought maybe I am just a
> > little clumsy and try a 1/32 bit and snap it. Noticeing that the
bit
> > did not penetrate all the way, I thought maybe I needed a backer.
> > Still no success and I snap another 1/32 bit.
> > 
> > My guess is that the dremel just has too much slop for these
bits. Any
> > suggestions. 
> > 
> 
> 
>    Wrote this the other day and saved as draft and didn't send it
later. 
>   There are a few aspects of using small bits to always keep in
mind 
> that don't normally matter with larger bits.
> 
> 
> 
>    You need to search through the old messages for mine on aligning
> double sided boards with drill bits and drilling holes, I've really
> explained how I do both cheap and simple within the last couple of
> months or so.  Several others also suggested similar techniques on
> aligning double sided, there is plenty to read.
> 
>     For the drills the answer is:
> 
>           "SPEED!!!"
> 
>    Almost guaranteed you are pushing down too fast for how slow the
> drill is turning.  Your feed rate has to be in scale with the tip
> cutting rate, and even with 20K RPM the cutting rate of the nearly
> microscopic
> diameter bits is rather low.  If you push a #80 bit in the same
rate as
> a .039" at the same RPM then you're going about 3 times faster for
the
> speed it's cutting.  Even if you go half as fast on feed rate you're
> doing 1.5 times vs the cutting speed.  Note that the 30K RPM seems
like 
> a hell of a lot on a Dremel.  It is not too much for tiny bits. 
But 
> it's nerve racking to hear so I normally just slow the feed down. 
Also 
> note you create ultrafine dust when you use small bits at high
speed 
> correctly, be sure and avoid and contain it as much as possible.
> 
>    Chuck up a #56 or #64 bit.  Now jam it into a board as fast as
you
> can with the drill press and see if it doesn't break too.  Even your
> slowest hand movements are close to this with the much smaller bit.
 And
> hand motion is irregular, even if you make the overall motion very
slow
> it's jerky when going through a material.  Uneven material makes for
> jerky motion as it catches.  It is very difficult to get any real
life
> out of one of these bits without a better tool than a dremel drill
> press.  But nowhere is the problem slop, it's your hand motion on a
tool
> that isn't designed to give you the precision needed for these
bits.  Or
> poor alignment of the tool.  I can just barely use them reasonably
by
> hand on a much larger press by bracing my hand and doing the
smoothest
> slowest motion.  Dozens to hundreds of holes that way.  Even then I
> break far more than on my machine, they are too thin and brittle to
be
> reliably used by hand.
> 
>    You can drill hundreds to thousands of holes even with resharps.
 But
> you have to make something so you can do it well, a hand drill
> press just isn't it.
> 
>    And no, it's not slop either.  The thousandth or two isn't a
problem,
> it can be traced back to misuse of the bit, either too fast a feed
or
> misalignment.  Not slop, misalignment.  You must tweak it until the
> drill is exactly aligned with the motion of the press or slide.  The
> angle has to be exact, so the tip cuts a hole and the shaft goes
exactly
> through the hole.  Even a tiny bit off means the tip cuts in one
place
> and as you push down the shaft is pushed more and more into one
side of
> the hole.  The alignment was just as bad with a larger bit, they can
> just take the strain and side cut a bit better.  You cannot properly
> align with a larger bit, you simply won't see the errors until you
get a
> #80 or so in there.  That it cut ok with larger bits just means they
> could take it.  My homemade CNC has tons of play, I can probably
deflect
> the bit 1/4" or more in either direction by hand.  Yet it doesn't
snap
> bits, and its overall accuracy is rather high because it has so
little
> sideways forces when drilling.  And it is not only not impossible,
it's 
> quite easy to get superb alignment if that's what you set out to do.
 If 
> you don't bother, you'll be talking a lot about how your tools have
so 
> much play.
> 
>    Note that your approach to solving problems like this needs
adjusting
> too, not just this particular problem needs solving.  While you can
be
> slack with larger bits, there's an absolute assload of small
variables
> that come into play when you shrink the scale down so much and have
> substantially weaker bits.  Far too many to be making assumptions
like
> 'it's the drill' without even checking them.  Feed rate, tip speed,
and
> alignment are
> the three main factors for any drill, so most problems stem from
one of
> them not being correct.  Only rarely is a secondary factor at fault.
> 
>    Note that VERY OFTEN when others say they changed tools, and
that the
> new tool fixed it, they don't even LOOK for what the real problem
was.
> So what the new tool doesn't snap bits.  That does not mean that
the old
> tool had too much slop.  Far more likely that the new tool has
better
> basic alignment than much less play, and the owner just didn't
bother to
> correct the alignment of the first tool.  Or a better feed mechanism
> that lets them feed more smoothly.  I don't have these problems even
> though much of my equipment is homemade and has far more play than a
> dremel.  But I've precisely trued the alignment to the motion. 
Once the
> bit starts drilling it stays in the hole, couldn't care less if
there's
> a few thousandths of play in the tool after it starts.  Hole may be
a 
> few thousandths
> off from where it was supposed to be, but a little play doesn't
snap the
> bits.  Even a tiny misalignment vs motion does since it flexes the
tool
> on every rotation.
> 
>    As always, 'It's YOUR fault.'  Only when you've gone through
> EVERYTHING and absolutely proven that it's not your fault is it not.
> Then it just might be the tool.  Even then you're almost always
wrong
> and it really is still your fault.  Tools are inanimate objects, so
> hardly ever make any mistakes, unlike their owners.
> 
>    When something messes up for me, there is a list I follow.  Me,
then
> tool.  I hardly ever make it down the list to tool.  Really it's
about 
> ten different me's, then tool is number 11.  By doing so, and
> finding the real reasons and correcting whatever slip up led to the
> problem, you will quickly become very good with your tools.  Someone
> who's good with tools can make better items with crap tools than
someone
> who's crap with tools can with the best tools.  Work on learning the
> tools even better.  It's far less expensive than just buying better
> tools and noticably more effective.
> 
> Alan