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Sawing question


#1

Hopefully someone can help me. When piercing with a 5/0 saw blade,
will using a # 78 twist drill bit work so that there is no big hole
that has to be worked into the design. ie…the hole is the same
size as the line cut and doesn’t have a big starting hole. Also are
there any # 78 twist drill bits with a standard or normal size shank
that will fit in a regular drill press without falling out? Any help
on this would be great!! Thanks in advance!-

Kristin


#2

Hi Kristin,

The short answer to your question is no. You’ll pretty much always
have a hole, just perhaps a very small one.

I don’t know off the top of my head how big a #5/0 blade should be
(manufacturers vary), but blades are rectangular in cross section.
If you cut it in half, and look “down” the length, you’d see that the
blade (even a teeny one) is taller than it is wide. So any drill bit
that gives you a hole tall enough to get a blade through will end up
giving a hole that’s wider than the blade kerf. This isn’t to say
that the holes can’t be made very small, and dealt with in one
fashion or another, but they’ll be there.

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.)

You can get a sensitive drill adaptor here:

http://www.ganoksin.com/gnkurl/xu

(Standard disclaimers apply: just a satisfied customer) (You can find
similar items by searching on “sensitive drill adapter”)

Regards,
Brian


#3

Hello Kristin,

The theoretical answer is “NO”. A 5/0 saw blade isn’t square; it’s
0.0080" wide by 0.0157" deep so a hole big enough to accept the
0.0157" depth will be 0.0077" wider than the saw cut - almost twice
as wide. BUT, bear in mind that any sharp change in direction of a
cut will actually require that the blade itself makes a wider cut,
then possibly it will make little or no practical difference.

Regards, Gary Wooding


#4

To fit in a standard drill press you will need to use a collet for
small bits. They are available from many engineering suppliers. The
one I use is made by Eclipse- so you could do a site search for
"eclipse collets". You will also need to drill at a high speed
otherwise you will have problems with snagging that snaps the bits
very readily.

Nick Royall


#5
will using a # 78 twist drill bit work so that there is no big
hole that has to be worked into the design. ie...the hole is the
same size as the line cut 

In a word, no.

All jewelers saw blades (other than spiral wax blades or similar
round wire types) are thinner, side to side, than their depth, from
the front of the teeth to the back. So a hole large enough to insert
the blade will always be slightly wider than the minimum width of the
cut. But if you use a small blade size, and a suitable small as
possible sized drill, the hole won’t be “large”. If your cut has any
corners, you can hide the hole there without it being too obvious.
But it will still be wider than the blade. One way you sometimes
(not often) can get around this is if your cut will have a
substantial section which is very straight. You can buy very thin
seperating disks as thin as.006". Those make a cut roughly the same
width as an 8/0 blade, or not much wider. If you can cut a slot in
your metal to cut through the metal, and do your sawing from that
starting cut, then there need not be a round wider hole. But this
really only works when you’ve got a substantial section that will be
a straight cut, and even then, requires a steady hand with the
handpiece to cut a clean small slot right where you want it. It’s
also possible sometimes to similarly open up a very narrow slot to
start the blade in, with a sharp narrow knife graver. Again, not that
easy to do cleanly, and only works with thinner metal or the cut
will get too wide anyway due to the taper of the graver.

As to drill bits, you can indeed get drills with standard 3/32
shanks. The only trouble with these (made by busch or meisinger, or
other bur makers) is that they are made of the same vanadium steels
as other normal carbon steel burs, rather than made from tougher high
speed steel, so they break a little easier, and don’t stay sharp
quite as long as the HSS bits.

Peter


#6

Kristin,

As long as the hole you are drilling will accommodate the 5/0
sawblade, you are good to go. The tricky part will be threading your
blade through the tiny hole and getting your blade tightened in the
frame without snapping it.

For your drill bit issue, you might try a pin vice, (very
inexpensive in a set of 5 sizes), to mount your #78 drill bit into,
and then mount your pin vice with drill bit into the chuck of the
drill press. I usually just mount the tiny drill bits into my
flex-shaft handpiece, brace my hands, and drill carefully, using a
dimple in the metal from a center punch to center the drill bit on
the metal.

They do make sets of standard sized shank drill bit shanks with very
tiny drill bit tips, but they are a bit pricey, and those tiny tips
break easily, in my experience.

Jay Whaley


#7

Alternatively, you could use a pin vise in the chuck to hold the
drill. I think the bearings will be a bigger problem.

RC


#8

Hi Jay,

As long as the hole you are drilling will accommodate the 5/0
sawblade, you are good to go. The tricky part will be threading
your blade through the tiny hole and getting your blade tightened
in the frame without snapping it. 

I’ll plug the Knew Concepts saw frame here, I’ve got the model
without the level, and I’ve managed to break one saw blade since I
received it, and that was only because I was trying to.

Regards Charles A.


#9

Kristin–

Also are there any # 78 twist drill bits with a standard or normal
size shank that will fit in a regular drill press without falling
out? Any help on this would be great!! 

When I use very small drill bits in my drill press I use an adapter
chuck. The adapter chuck has a shaft that you tighten into your
regular drill press chuck. At the bottom of the shaft is a chuck
that takes small bits. The adapter chuck can take a variety of small
bits and you don’t have to replace it when the drill bits break.
There are a lot of varieties available. I think you probably can find
something for less than $20. If you call the place you usually buy
tools they can probably point you in the right direction.

Whit


#10

Collets from a Dremel or other such tool can be chucked into your
drill press to hold smaller drill bits.

Jim
Blessed be…


#11

Brian,

You can get a sensitive drill adaptor here:
http://www.ganoksin.com/gnkurl/xu 

I got a kick out of the “related/suggested” items listed below that
adaptor.

First one is an “interstate” brand (probably chinese, but don’t
know) set of 61-80 drills. For about 16 bucks. Not the cheapest I’ve
seen, but not outlandish (I usually seem to find em on sale somewhere
for closer to ten bucks when I’m looking, if I look long enough)

But the third one? Similar looking set, but U.S. made. Same teensy
little 61-80 drills, same HSS metal, same TiN coating. But for these
babies, they wanted 225 dollars. 14 times as much. Sheesh. I think I
just found one example of possibly why the U.S. economy tends to
sometimes have trouble competing with overseas sources. Who in their
right minds, (other than NASA and the military, and maybe even not
them) would actually pay this much for these things? Would anyone on
Orchid? We’re not talking large or high tech drills. Just perhaps a
slightly more accurate product (though there’s nothing there to
suggest that) in drills that are still just as easy to break…

Maybe it’s just a misprint/type. Perhaps the decimal place should be
moved to the left one place. Dunno. Just caught my eye, for sure.

Peter


#12
I usually just mount the tiny drill bits into my flex-shaft
handpiece, brace my hands, and drill carefully, using a dimple in
the metal from a center punch to center the drill bit on the metal. 

And that is the only way to do it. Forget about drill presses,
expensive adapters, and the like. Learn to drill like a goldsmith,
using flexshaft. There is a technique involved in drilling with
flexshaft. I demonstrate the process in my DVD(s). Another thing is
that your drill is too small. #78 is equivalent to metric 0.45mm.
There is no need to use drill that small. #77 may appear almost the
same, but on that scale it is 10% of improvement in durability. Makes
all the difference.

You do not need to worry too much about having drill the same size
as thickness of saw blade. Slight enlargement is hidden either in the
corners, or beginnings and ends of cuts. It is even an aesthetically
required to have enlargements in these areas.

Leonid Surpin
www.studioarete.com


#13

I forgot to mention the old engineering trick of holding drills that
are too small for the chuck. You simply wind a coil of soft (copper,
iron, or whatever) wire around the shank - like a tight spring.
Choose a wire thick enough to allow the chuck to grip it securely.

Regards, Gary Wooding


#14

Just try drilling with both sets of drills and you’ll see the reason
for the price difference pretty quick. Quality is expensive.

RC


#15

Hi Peter,

I tend to agree with you on the “WTF” factor with that particular
price, but there are reasons why one might choose to pay much, much
more for a quality drillbit rather than just using the cheapest
random Chinese crap. Production being the obvious answer.

For the drills and taps Lee and I use for the clamps on the KC saws,
we’re using drillbits that cost $30 each (in bulk), for a 1/16" bit.
No, that wasn’t a typo. $30 EACH. Equally, the little drills that do
the hole for the blade cost in the neighborhood of $15 each. (and
the taps are about $15 a shot as well.)

The reason we go with those insanely expensive bits is that they
LAST, and that they’ll let us cut faster, which in the long run,
makes them much cheaper.

Figure it takes me 5 minutes to change and re-zero a blown drillbit,
plus another 5 minutes to hand edit the program to skip to the next
undone section, and avoid the part with the busted bit in it, that’s
10 minutes per blown bit. At $200/hr for the machine, that’s $33 in
time per blown bit. The $30 bits last, on average, something like
500 parts, while the best we were getting before, even with name
brand US bits was something on the order of 80 parts per bit. That’s
about 6/1, so figure the normal bits would have cost me $200 in time,
nevermind the scrapped parts. The $30 bits also let me boost my
drilling speed by 1/3, so I’m saving $200 in changeout time, plus
1/3 on the cutting time. (figure 180 minutes saved over 500 parts,
roughly. That’s $600 in time savings.) Add that together, and you
save $800 per bit, by using what would seem to be insanely expensive
bits. Looked at in that light, I can’t afford not to use them.

Once you get into CNC and production, a lot of those “holy crap
that’s expensive!” tools and bits suddenly start making a whole lot
more sense.

Regards, Brian

PS–> I’ve used Interstate taps…NEVER again. Ever. They’re
actually coming out of former Yugoslavia somewhere, but they’re
incredibly brittle. At one point, I blew 6 of them in a row rigid
tapping on some 8/32’s Six holes, six blown taps. I switched out to
decent Balax taps, and did the next 80 or so without a single
problem. (So it wasn’t the program or the machine, it was the taps.)


#16
Once you get into CNC and production, a lot of those "holy crap
that's expensive!" tools and bits suddenly start making a whole
lot more sense. 

I do not do CNC, but I use the most expensive drills I can find.
There are tasks when breaking a drill means tossing you work into
scrap pile and starting again. Design that I have used for my latest
DVD “Ballerina Ring” is a good example. If drill breaks while
drilling in narrow end of a stone region, chances are that the whole
thing needed to be redone.

Another example is working on pave models for 1mm stones. Holes are
drilled with 0.5mm. The casting comes back with approximately 0.6mm
holes. They needed to be re-drilled which brings their size to 0.7mm.
That is the maximum allowed for 1mm stones. Anything larger and
setting becomes very difficult. For production lines it is not
acceptable.

If drill breaks, one cannot help but to enlarge the hole slightly
while getting it out (if possible at all) and that enlargement puts
viability of whole work in question. No matter how expensive a drill
it, it is a bargain compared to the trouble that cheap drill can get
you into.

Leonid Surpin
www.studioarete.com


#17
If drill breaks, one cannot help but to enlarge the hole slightly
while getting it out (if possible at all) and that enlargement
puts viability of whole work in question. 

Leonid, if your model is made of any metal that can withstand normal
sparex pickle, just mix up some fresh strong pickle (sparex or
better, one of the purer brands or just plain sodium bisulphate)
Pewter doesn’t much like the stuff, but everything else I’ve used for
models, including nickle silver, will generally withstand it. perhaps
there are some jewelry model metals somewhere that won’t, but I’ve
not had that problem yet. The hot, even boiling, pickle will
dissolve any carbon or high speed steel, and even seems equally
effective on carbide bits. Getting the broken drills out without
making the hole larger is possible. The real question is whether in
the act of breaking, that event itself caused too much damage. In
that event, you may find, finally, a good use for a laser welder (or
more likely, a favor from a friend who has one, if you don’t. Fill
the damaged hole, redrill carefully…)

Normally, I wouldn’t presume to give you techincal advice like this,
since you rarely if ever are in need. But it occurs to me that
breaking drills may be rare enough for you that you may have
forgotton this trick…

Easier, of course, is your method. Being careful and exact enough
and using good enough drills that you don’t break em in the first
place…

cheers
Peter


#18
I forgot to mention the old engineering trick of holding drills
that are too small for the chuck. You simply wind a coil of soft
(copper, iron, or whatever) wire around the shank - like a tight
spring. Choose a wire thick enough to allow the chuck to grip it
securely. 

For the tiniest drills I’d been applying tape to the shaft for the
same problem but fiddling with adherence and trimming is
time-consuming. This solution is so-oo much easier. Thanks Mr.
Wooding!!!

I’ve also used the mini-chuck adapter with 3/32" shank in flex
shaft. For safety please cut the shank of this adapter as short as
possible before using.

My best,
Pam
songofthephoenix.com


#19

While we are talking about sawing, does anyone have any advice on
saw blades, where to buy, what to look out for, brands to seek or
avoid? In in the UK, but I’m sure this issue is of interest to
everyone around the world.

Best one’s I’ve used have been Pike brand, made in the US, with
milled teeth. Usually well tempered, too. Quite expensive, but worth
it. AF and Vallorbe are the most common in the Jewellery Quarter
trade shops, but they are stamped, and give me no end of trouble.
One characteristic of these seems to be a residue of the stamping
process down one side of the blade. In extreme cases, these can cut
off-centre straight out of the packet. I’ve even had batches where
the lengths were all different! To quote a chap called Joe Escott:
“Made in Switzerland? I didn’t know Switzerland was in China!”

Jamie Hall
http://primitive.ganoksin.com


#20
The hot, even boiling, pickle will dissolve any carbon or high
speed steel, and even seems equally effective on carbide bits.
Getting the broken drills out without making the hole larger is
possible. 

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.

Consider scenario of drill breakage. Pave model for 1mm stones - 1.2
to 1.5mm in thickness ( variations due to your confidence in your
caster ), moderately domed. That means that exit holes are smaller
than entry ones.

The most dangerous phase of drilling is when drill is about to break
through, and that is when it usually breaks at the point about 1mm
above the surface. The drill is not completely through, so there is
only one avenue for acid attack. The broken piece is about 2mm thick,
with more than half of it completely enclosed in silver.

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.

The way it usually done is to anneal the piece. Using center punch
from inside the broken piece is dislodged up towards the entry. This
accomplishes 3 things. It open access from the inside, so acid now
can attack from 2 directions. It exposes broken part of the drill to
larger degree acceleration the process, and it create spaces between
broken part and drill channel to allow acid to penetrate deeper. In
another words, now we can accomplish dissolving the drill in
reasonable time. The only problem is that center punching enlarges
the hole on the inside. For 2 pointers and up, it has no detrimental
effects. It is problematic for 1 pointers, and it is deadly for
anything bellow. And now you have the whole story.

Leonid Surpin
www.studioarete.com