Sawing question

Jewelry Discussion
21 
Very popular advice. It makes sense from the point of chemistry,
but if we ask a question "how long is it going to take", it is
rarely useful.

I’ll refrain from quoting the rest of your long and detailed reply,
Leonid, but will say that I’ve broken my fair share of bits, exactly
as you describe, in metal just as thick, sometimes thicker. Typical
broken drills will be dissolved via my described method in anywhere
from 15 minutes to an hour, depending on just how much metal is
there. Almost never takes longer than that. The times you descirbe,
I’d agree would be too long. Overnight? If it took that long, I too
would be reaching for the centerpunch. Another trick I’ve sometimes
used is with the laser welder. Set to high power, very tight focus
(small spot), and a very short pulse length, the laser makes a
halfway decent drill for imprecise pilot holes. Useful for blasting
out bits of remaining ceramic-hard platinum casting investment too,
which otherwise destroys bits. Anyway, with the drill bits, blast
through the hole with the laser. This welds steel to your metal too,
which isn’t desired. But then the pickle gets the job done faster,
removing the steel and leaving a pilot hole. However, though this
method can be useful, generally, I use it only when I suspect
something hard (like that investment inclusion) was the cause of the
breakage. Otherwise, I just let the pickle do it’s thing. And as I
say, it doesn’t seem to take as long for me, as you seem to have
experienced. Try mixing up the pickle stronger, and be sure it’s
hot.

Note that I mix the pickle solution fairly strong. While still cold,
a tiny drop on a fingertip, tasted, will be uncomfortably sour
tasting, but won’t actually burn. (and yes, this is reasonably safe
to do. spit it out and rinse, and you’re fine. Don’t do this with
electroplating solutions, of course… :slight_smile: ) I know that’s not an
accurate recipe of how strong to mix it, but it’s a useful quick
check.

As well, for removing drill bits, the solution is boiling, or almost
so. You can speed it up even more by suspending the beaker with hot
pickle in an ultrasonic cleaner. That can cut the time in half, as
ultrasonic cleaners concentrate their activity in holes, greatly
increasing the aggressiveness of the acid attack on the steel.

Cheers
Peter

22

As far as gripping teeny drills, that’s the fault of the chuck on
whatever drill press you’re using. #78 drills are small. Most
generic household drillpresses are really intended for weekend
warrior types, using them to drill holes in angle iron, so they like
nice big drill bits. The bearings on a generic DP may not be
accurate enough to run a #78 without breaking it. (eccentricity
(while fun in people) breaks teeny drillbits instantly.)

(The reason I worry about your bearings is that most good quality
chucks could at least hang onto a #78 bit, if not happily. The fact
that yours can’t implies that the whole machine may have other
issues.) Step one would be to get either a sensitive drill adaptor,
or a better chuck. If you centerpunch the metal carefully, and still
have trouble snapping teeny little bits like that, then it’s time to
look to a better DP. (The problem with that is that ‘serious’ micro
drill presses are in the $1000+ range.) " This advice is correct and
very helpful. However, the problem is not just the chuck and a
higher precison chuck will not necessarily solve the problem. Rather
it’s the whole mechanism that moves the chuck up and down relative to
the motor and work table, what is sometimes called the quill. On your
typical, large shop drill presses this mechanism just has too much
slop in it. And this slop become exaggerated when the quill is
extended to move the chuck and bit down closer to the work. The more
the quill is run out the greater the wobblies that occur. In a
precision drill press the mechanism that moves the quill is of
higher precision (hence the name). Sometimes this precision is
achieved by having the motor, pulley, shaft, and quill all move up
and down as a unit, thus obviating one source of possible slop. So,
the chuck adaptor being recommended will not solve the problem if the
quill into which the adaptor is mounted has the wobblies that most
shop drills have built into them. As suggested, the best solution is
a good precision drill press. And while you can find any number of
inexpensive “small”/“micro” drill presses, especially Chinese junk
for around $50, what you want is a PRECISION drill press. You need a
rock-solid quill-lowering mechanism and high rpms for tiny bits.
(And, of course, a nice soft touch in using it, as any
ham-fistedness will still break bits!) An ideal set-up is a precision
CNC milling machine, but the y are very expensive (thousands). For
alternatives Proxxon makes a good-quality 3-speed micro press for
about $200. It uses a rack and pinion mechainism to move the quill,
but it’s pretty good quality. However, it uses a non-adjustable
collet (as opposed to an adjustable Jacobs chuck), so all your micro
bits have to have the standard shank that fits that collet (5/32
inch, I believe). This fixed collet helps minimizes the wobblies even
more by eliminating an adjustable chuck, but the bits are expensive.
However, they also seem to be the manufacturer of the dandy little
drill press that MicroMark sells under it’s own name (Micro-Lux),
with an adjustable no. “0” Jacobs chuck. And they also sell a dandy
compound X-Y table that fits on the drill press so you can space very
accurately those tiny holes if you need them lined up in a row (a la
pave stone setting). The drill press sells for about $$170 and the
X-Y table another $90 or so. (see:
MicroLux® 3-Speed Mini Drill Press). If you can find a used Cameron
drill at a reasonable price, go for it. They make a whole series of
drill presses with speeds up to 30,000 rpm, both manual general drill
presses and highly automated, highly customized versions. (see:
http://www.ganoksin.com/gnkurl/yb). In the manual presses, the whole
motor/pulley/shaft/quill/chuck assembly moves up and down as a unit.
But they are pretty pricey new. I picked up one at a surplus sale of
a medical lab where they had used it to drill hair-thin holes in
catheters. It also has the no. “0” jacobs chuck. I got a deal at only
$260 for it but had to drive 120 miles to pick it up. Otto Frie
appears to be selling Cameron drill presses as their “Precision Micro
Drill Press” for about $900. Not cheap. But hard to do better. Dumore
has been making a small precision drill press for many years. You can
sometimes find them on Ebay quite reasonably and even the older ones
work quite well. And, of course, they sell new ones. They use an
adjustable Jacobs chuck. On the older models they deal with removing
the wobblies in the quill by keeping the motor, pulley and quill
stationary and, instead, having the table that holds the work move up
and down to meet the bit, instead of the the traditional method of
having a quill that moves up and down to a stationary table. The
small table is round and only about three inches across. You raise
and lower the table by turning a knurled knob and you have to hold
the knob to keep table in position while drilling. Otherwise it
drops. It’s a solid, very compact tool. I recently was looking for a
good precision drill press for the San Diego Mineral and Gem Society
(where I teach jewelry arts). After some research and searching I
found and bought all three of the above machines, took 'em into the
studio, and had all the other instructors try them out. In the end
the consensus was that the MicroMark machine was best for us. The
cost was reasonable for a new one and the machine was easy to use and
store, and we liked the Jacobs chuck over the fixed collet version.
The Cameron was larger, had some attachments used by the provious
owner we didn’t need, and was a little intimidating with the dial
gauge and fine adjustment mechanisms. And it didn’t fit into the
storage cabinet we had. The (abeit older) Dumore was solid and
compact, but sounded like a Mixmaster (very loud) and was a little
hard to use: holding work on the table while moving the table up and
down sometimes introduced movement in the work, thus negating the
otherwise fine precision of the drill. I sold the Dumore and kept the
Cameron for myself. However, I’m finding when I just want to drill a
small hole quickly, I grab my own MicroMark off the shelf and use it
over the Cameron. It’s faster than setting up the Cameron and faster
and certainly more accurate than using a flex shaft.

Denny Turner

23 
You can speed it up even more by suspending the beaker with hot
pickle in an ultrasonic cleaner. That can cut the time in half, as
ultrasonic cleaners concentrate their activity in holes, greatly
increasing the aggressiveness of the acid attack on the steel.

That I have never tried, but makes perfect sense. Solution
constantly moving, by product are removed, and fresh metal is
constantly exposed. That should definitely speed things up.

Leonid Surpin

24 
Exposed part will be dissolved relatively quickly, but the
enclosed part is something else. Just dropping it in jar of acid
for overnight bath is not effective. Acid reacts with surface
layer, but than reaction by-products covering up the surface and
reaction stops. Piece needed to be inverted and solution should be
constantly agitated for reaction to continue. Such conditions are
easily created in chemical labs, but very very difficult in the
goldsmith shop. I do not have such equipment. So here goes the
theory of boiling out.

No lab needed just put item in small glass jar with pickle in it in
ultrasonic basket it will be gone within an hour without screwing up
your work.

James Binnion
James Binnion Metal Arts

25

Or you could use a magnetic stirrer.

John
Rasmussen Gems & Jewelry LLC

26 
That I have never tried, but makes perfect sense. Solution
constantly moving, by product are removed, and fresh metal is
constantly exposed. That should definitely speed things up.

It does. Try it. An I must say I’m delighted to have finally offered
a suggestion here on Orchid that you, Leonid, seem to find
potentially useful. That makes me happy. More fun than arguing or
debating esoteric minutae…

One thing I should have mentioned. Especially if your pickle in the
ultrasonic is hot, but even if not, I’d suggest covering it, so as to
avoid generating any aerosol mists of the pickle due to the
ultrasonic action. Some ultrasonics are powerful enough to do this,
with some solutions susceptible to this effect (it differs with the
type of solution, and I suspect pickle or other acids may be more
prone to this than the common cleaning solutions) The point is
essentially the usual cautions regarding ventilation should be
observed. I don’t really want to be breathing hot pickle aerosol
mists…

And not so much addressed to Leonid, whom I assume knows all this,
but to others who might find this interesting…:

I’ve become rather more attentive to ventilation issues over the
last year. My employer moved locations two years ago when the
previous building we were in changed owners and the new ones wanted
to almost triple the rent. The new location has somewhat less access
to open windows and vents in the shop area. The room we now use for
casting in particular has what I consider inadequate ventilation. It
amounts to a rather small sized bathroom fan sized vent in the
ceiling, which is then driven by an exhaust fan located midway in
the round ducting leading to the outside. Just not very powerful
airflow, even if technically it does change the air in the room
(though I have no idea how long it takes). In any case, part of my
job is often doing the investing for our gold and silver casting,
using Satin cast 20, which of course contains silica, as do all such
investments. Accordingly, I’ve always used a decent (I thought) N95
face mask, the paper sort with a vent made by 3M. It’s often sold as
suitable for this type of use, but I find it not terribly
comfortable, and suspect it doesn’t seal well to my face (or I
wouldn’t occasionally find my glasses fogging up…)

Anyway, the fall before we moved, a year and a half ago, now, I’d had
a bad cold, with a cough, and all the usual sinus issues. It was
still lingering when we moved. And though the cold cleared up, the
sinus issues, and the annoying chronic cough, never went away. Docs
confirmed it was sinus, not infection, and couldn’t find any
allergy, though I had my suspicions they just didn’t find it. Various
pills didn’t help, and sinus rinsing (a not very pleasant procedure)
helped on some, for a short time each day. I was going a bit nuts
with that cough (as if I weren’t already nuts, as you all must well
know by now). I suspected something in the air in our new building,
but inspectors say the air is fine (they tested, since parts of the
outside of the building have paint contaminated with PCBs, which are
being removed)

But then, on a hunch, I bought a better mask for investing and
working in the casting room. This is one of the 3M half face
cartrige type respirators, fitted with P100 cartriges (rated almost
100 percent particulate filtration as opposed to the 95 percent
rating of the paper N95 masks. And guess what. Wearing this
respirator when I do the investing resulted in my chronic cough and
draining sinuses clearing up within a month. Really surprised me how
fast, and how clear the change was, as well as the difference between
these two types of protection. The bottom line is that if by chance
you’re cavalier with ventilation (maybe you think you’re younger and
healthier than my 59 years with a lifetime of type 1 diabetes, so it
doesn’t matter for you yet…), you may be exposing yourself to more
risks and potentially harmful materials than you realize. Don’t take
chances. By the time you realize from symptoms that you should have
been more careful, you may not be as lucky as I was in finding my
symptoms clearing up…

:slight_smile:

Peter

27 
broken drills will be dissolved via my described method in
anywhere from 15 minutes to an hour, depending on just how much
metal is there. Almost never takes longer than that.

This is my experience also. Boil til the bubbles stop. Cheers Peter.
Thanks for putting forward yet again your sensible and practical
advice.

Brian
Auckland
New Zealand
www.adam.co.nz

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