I do like that idea of a counter balance - it adds feedback to the
drilling process. There are small precision drill presses that have
some sort of device on them for very precise small hole drilling in
metals. I have seen them, never touched one so I don't understand
it completely. But, from what I gather it works something like
this...
It has a quil like a drill press, but no arms. To move the tool up
and down it has some sort of collar located just above the chuck
(this collar does not rotate). To move the drill bit, pull this
collar down to feed the bit into the work - very tactile and works
pretty good from what I saw. The operators work with stereo
microscopes so they can see what is going on. For me, this sort of
work would drive me crazy in a couple of hours - probably minutes!
Chris
--- In
Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@g...> wrote:
>
> I agree on all points.
> With a large press and the friction and spring pressure involved
in the
> pinion feed, and the good lever action, makes for practically
zero
> feedback about the force on the drill (and that is tiny in the
first place
> because of the size).
> Before i put a vice as counterweight on the back of my pivoting
press the
> weight of the arm and spindle would feed the drill too fast,
especially at
> low RPMs, which broke a drill. Now that it is balanced i get a
very good
> feedback of force from it, i guess the counterweight is a bit
better here
> than a spring, and the almost frictionless thrust bearings help
too.
> There's definitely a difference in "drag" between a fresh out of
the box
> drill and a well used one, although the holes will still be nice
and clean
> with a slightly dull drill and i see no reason to stop using it.
>
>
> If you feed slow enough for the RPM, and board and spindle is
solid, and
> there's not too much runout, the drills won't break, of course.
But
> carbide drills are about the most brittle drill one will ever work
with,
> and usually the smallest too, so it takes some attention to get it
right.
>
> I have tried different arrangements, including a spindle holder
for a
> drill stand inctended for normal power drills, and nothing worked
really
> well. The pivoting press does what i need - hold the drill exactly
upright
> and in place while allowing me to feed it freely. With it i only
break
> drills when making mistakes.
>
> Anyway, it's not a problem, but it isn't the same as drilling a
8mm hole
> in a piece of wood either.
>
> ST
>
> On Sat, 17 Dec 2005 13:20:24 +0100, lcdpublishing
> <lcdpublishing@y...> wrote:
>
> > While I am/was a machinist and have plenty of experience drilling
> > holes with a wide variety of tools, I am very new to drilling in
PCB
> > materal. I have only drilled a thousand or so holes so far.
> >
> > However, what I have learned is that the same rules apply to
> > drilling PCBs as any other thin material - with one exception
which
> > I will explan last....
> >
> >
> > Speed isn't that critical for PCB material - It drills fine at
800
> > RPM and at 3500 RPM and at 20,000 RPM. When drilling on my drill
> > press, I use around 1500 RPM or so, it's quiet and works well.
The
> > more RPM does help, but isnt' critical. Adjust your rate of feed
> > accordingly with the RPM.
> >
> > Stable backer board and hold the PCB down. MDF makes a good
backer
> > board to rest the PCB on and to drill into - It's cheap. As the
> > drill bit breaks through the back side of the board, it will
have a
> > tendancy to lift the PCB up, hold the PCB down to prevent this.
> >
> > Exception -----
> >
> > When drilling the PCBs on a drill press and positioning the work
by
> > hand, it is very natural for someone to get the spot lined up,
then
> > quickly pull down on the handle. PCB is soft and drills easy so
the
> > assumption is to drill quickly. As you get tired, this tendancy
to
> > feed quickly also increases. This is probably the biggest cause
of
> > broken drill bits.
> >
> > When drilling hard woods or more so with metal, there is "feed
back"
> > in the lever to indicate you are feeding with enough presure,
with
> > PCBs this isn't very noticable. So, to help guide you a bit, try
> > this the next time you sit down at the drill press.
> >
> > Line up the part with the drill bit, gently pull down on the
handle
> > until the bit contacts the part. Now, try to time the cut to
last 1
> > second - no less. You will notice right away this is about 10
times
> > longer than you naturally been doing it AND you will also notice
> > that the part has much less tendancy to lift off the drill press
> > table.
> >
> > Practice that for a while and you should see a difference right
> > away. As for broken bits for me when drilling PCB material....
> >
> > So far this is what has broken the bits for me...
> >
> > 1) Dropped on floor
> >
> > 2) Poked hole in finger while trying to get it out of the little
> > box, not once, but twice. The second time it stuck in my finger
and
> > when I pulled back in pain, it stuck and flew against the wall.
> >
> > 3) Kept drilling after I was tired (probably 40 holes or so) and
> > didn't feed slowly enough and the PCB rode up the drill bit.
Then in
> > reaction, I pushed the board back down and bit broke
> >
> > 4) I tried to drill a hole free-hand with a dremel - bit broke
> >
> > 5) I lifted the part up off the drill press table without first
> > sliding it out from under the bit - bit broke
> >
> > 6) I tried to drill a hole in a PCB at the drill press but with
most
> > of the components installed on the board. The board would not sit
> > flat during drilling and the drill broke.
> >
> > I believe that pretty much sums up my experience so far with
> > drilling PCBs.
> >
> > Chris
> >
> >
> >
> >
> >
> > --- In Homebrew_PCBs@yahoogroups.com, Mycroft2152
<mycroft2152@y...>
> > wrote:
> >>
> >> As strange aas it may seem, in my supporting Stefan,
> >> bits do break and often. Stefan is not a klutz. :)
> >>
> >> I thinks it's a difference in perspective, if you are
> >> a machinist, with the right tools, knowing the correct
> >> procedures and used to machining steel; drilling a few
> >> holes in epoxy fiberglass is easy.
> >>
> >> For the rest of use who are weekend warriors, drilling
> >> ususally means putting few holes in a 2 x 4, it's
> >> difficult to downsize the procedure.
> >>
> >> what may be a 'hair off' to the weekend builder, will
> >> look like the grand canyon to the experienced
> >> machinist. Combined with the diffence in tool
> >> sharpening (if ever), it all adds up to drill
> >> breakage. At the low cost of drills, it's not a big
> >> deal to the weekend builder.
> >>
> >> TANSTAAFL
> >>
> >> Myc
> >
> >
> >
> >
> >
> >
> >
> >
> > Be sure to visit the group home and check for new Links, Files,
and
> > Photos:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> >
> > If Files or Photos are running short of space, post them here:
> > http://groups.yahoo.com/group/Homebrew_PCBs_Archives/
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
>