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Slow drilling using a flex shaft


#1

Drilling question from beginner

I have been using a flex shaft and small drill bit (#60) to drill
holes in 20 g copper. It seems to take forever to get through the
metal on most occasions.

I’m not sure if it is the drill bit being dull, my technique (speed
used, pressure,…). I ding the spot prior to make a dent. Are
certain drill bits much better?

I tried to make the initial opening with a reamer type tool. It goes
through better, but I would like the precise diameter of the drill
bit.

I want to be able to put alot of decorative holes in some of my
work, but it is taking me so long to do several. Figure I must be
doing something incorrectly.

So hints and suggestions are welcome.
Thank you.
Jamie


#2

since you asked the question “Are certain drill bits much better?” I
have to ask, are you using a metal drill bit versus a wood drill bit
(both are made of metal, name is used to designate what they should
be drilling through, just as there masonry bits also)?

also while drilling metal, as you using any lubricant to lessen heat
damage to your bit?

john
John Atwell Rasmussen
Rasmussen Gems and Jewelry
www.rasmussengems.com


#3

Small drill bits need really high speeds to cut correctly. The
recommended speed for a #60 drill bit in copper is 10,000-20,000 RPM
(100-200 Surface Feet per Minute). This obviously is quite fast and
it can be very difficult to control a hand held drill at this speed,
but the closer you get to this speed the better results you will
have from the drill bit. If you have access to a drill press mount
for your flex shaft hand piece it will be much easier to drill these
small holes rapidly and cleanly.

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#4
I have been using a flex shaft and small drill bit (#60) to drill
holes in 20 g copper. It seems to take forever to get through the
metal on most occasions. 

High quality drill bits generally will give better results. Be sure
you’re getting good high speed steel bits, and preferably, from a
major manufacturer. I bought some once on ebay that seemed a great
deal. Good steel, but not a good grind nor well sharpened. Worthless
drills for a bargain price aren’t a bargain. So anyway. Get high
quality drill bits and you’ll see much faster drilling.

Also, be sure to use a lubricant of some sort. Bur life, bees wax,
ordinary machine oil, or even saliva will all not only help to keep
the bit cool, but will speed up the cutting markedly.

Dinging the metal first may not be quite enough to give the bit a
good start. Use a center punch, which puts an actually conical
depression in the metal. Gives a solidly located hole since the bit
will be less likely to wander around a bit before biting into the
metal.

If, while drilling, the “feel” changes, seeing coarser or the bit
seems to be slowing down, pull it back slightly to allow more lube to
get into the hole before resuming. This also allows the chip to break
free, and the hole to clear out a bit before you continue, again
helping the lubricant to get into the hole.

If the drill bit heats up and discolors during use, you’re either
not using lube, or more likely the drill is dull and needs
resharpening or replacing.

I’d expect that your holes might take somewhere in the area of ten
seconds each, to drill, if all the above are done.

HTH
Peter


#5
I'm not sure if it is the drill bit being dull, my technique
(speed used, pressure,...). I ding the spot prior to make a dent.
Are certain drill bits much better? 

Copper is tough to drill no matter what. Speed, pressure are
important. Also the way drill sharpened is a factor. As a rule, the
softer the metal, the more acute angle of attack. However, if you
would adjust angle of attack, it could be too much for a small drill,
especially since you drilling by hand.

You can try this trick.

Mark holes with center punch. There must be metal plate underneath
copper sheet. You do not want to distort the shape. After that take
another center punch with much larger angle, let’s say 120 degrees
and go over marked holes. Done correctly there should be no
protrusions on the other side of the sheet. If number of holes is
large, the sheet could start curving a bit, but that could be
corrected later. What you are trying to do is to work harden copper
in the areas of the drilling. Also it would reduce the effective
gage of the sheet in the drilling areas and it should speed things
up.

Leonid Surpin
www.studioarete.com


#6

You are doing something incorrectly.

One solution is to use a “Foredom” DP-30 drill press for which
you’ll need a #30 handpiece to hold the drill. And “Tap Magic cutting
fluid”, just a drop will do it, little pressure, and use a drill
punch available at any hardware store to give the drill a starting
point. These details for small drills should make it easier.

Just one way; not the only way.

KPK


#7

I do a lot of drilling with my flex shaft, and you should not be
having that much trouble. Are you using a good brand of drill bit?
You might also try drilling into a block of wax, then into your
metal - sometimes that helps. What do you have under the metal to
drill into? I place my metal on a block of scrap wood. I really
suspect it is all down to the quality of your drill bit though!

Beth in SC


#8

Jamie -

Here are a few possibilities:

  1. The copper has not been annealed first. (Check the archives for
    procedures.)

  2. The ‘ding’ you put in the metal is really compressing the spot -
    although your bit won’t wander, it now has a work-hardened spot to
    drill through. Either make the ding first then anneal, or use a small
    ball bur to make the ding. No compressed metal, and the bit has
    something to bite on as it starts. It also doesn’t deform the metal,
    where it becomes an unsightly mark on the back of your piece.

  3. Your drill bit is dull or has lost its temper (no pun intended!).
    If you have been drilling with limited success, it may be that your
    bit was OK at first, but got overheated and soft.

Use a new bit and lubricate it before every use. (Burr Life,
beeswax or an old candle will do.) Don’t let heat build up. Use a
slow speed on the flexshaft. High speed will only create heat faster
and promote breakage. Slow speed allows greater control, especially
on breakout at the back. And wiggle the bit a little as you drill -
don’t go to town on this! You don’t want an oval hole, or a broken
bit. The wiggle is just enough to help present new material to the
leading edge of the bit down at the tip, and clear out the scrap as
you drill. (There was some on this recently in Art
Jewelry or Jewelry Artist/LJ, can’t remember which.)

I recommend that you use a piece of scrap metal as a backer plate
during drilling, to minimize ragged edges on the exit holes.

I hope all this helps you,
Kelley


#9

Using a lubricant on the drill bit will help it run without getting
hot and possibly breaking. Also, the bit could be dull.

Susan
www.ThorntonStudioJewelry.com


#10

Hi Jamie,

Karen here, author of the Flex-shaft book.

You have a dull drill bit. A sharp bit will chew its way through
copper with no problems. For the perfectly drilled hole, follow these
directions.

  1. Make a tiny dent with either an automatic center punch found at
    any tool supplier, or even a nail and hammer. This creates a guide
    for the drill bit so it won’t skip over the metal.

  2. Lube your bit with Bur Life (waxy stick) or better the liquid
    variety, Bur Lube. A quick dip will do you fine. The feature of the
    liquid type is that not only do you create lubrication for your bit,
    but you maintain the sharp edges, causing the drill bit to "rip"
    through the metal. Just dab of the excess or spin it off in another
    container.

  3. Once you have drilled through your metal, every other time you
    drill, dunk your drill bit in the lubricant and pulse the flexshaft
    just a little. The centrifugal action will spin off any loose metal
    bits and they will fall to the bottom of your container. Grit or
    metal shards will dull your drill bit quickly. The stick variety of
    lubricant is good for sawblades, but NOT drill bits or burs. If you
    plunge a clogged bur into the hardened lubricant, you are just
    transferring more grit back to the source. You need it OFF your drill
    bit or bur so it can continue staying sharp and doing its job.

  4. Drill your hole. You will see a marked difference in a dull bit
    and a sharp one.

  5. What are the best drill bits? Preferably, I like HSS which stands
    for High Speed Steel which are sharp and last longer, provide you
    take care of them. They are a little more expensive, but they last
    longer under higher speeds and friction.

Lastly, when you are at the “dent”, make sure your drill bit is
moving. You will ensure that the guide will do its job and you need a
smaller dent. Keep a light hand on the handpiece and then lightly
push. Let the drill bit do its job.

Hope this helps!
k


#11

never buy chinese drills, only usa, or germany, also best to get
them from jewelers supply, or machine shop supply, china does have
the ability to make great steel that will hold an edge, but you
will never see that quality unless you shop there and know what you
are looking for

dp


#12
Either make the ding first then anneal, or use a small ball bur to
make the ding. No compressed metal, and the bit has something to
bite on as it starts. It also doesn't deform the metal, where it
becomes an unsightly mark on the back of your piece. 

Most definitely NOT SO.

Compared to steel, copper, even in its most work hardened state, is
very soft indeed. Work hardened copper is actually easier to machine
than annealed copper. In its annealed state, it is very soft and
"cloying" and tends to stick to the cutting edge of any tool you use.
It clogs files and saws, and builds up on the edge of drills making
them appear dull. It doesn’t actually blunt the tool (drill bit),
instead it sticks and partially welds itself to the cutting edge,
thus covering it up. Most aluminium does the same.

Clogged files don’t cut and appear to tear the metal, and clogged
saws tend to drag horribly. Copper is not a nice metal to machine.
Work hardening helps a bit, but with copper you MUST use a lubricant
to minimize the build up.

The ‘ding’ will have no effect on the drilling operation other than
guiding the initial start so that the hole is drilled where you want
it. Use a small centre-punch (the automatic type is a real
convenience), use a lubricant and make sure to withdraw the drill
frequently so as to clear the swarf. This applies especially when
drilling deep holes - deeper than about 3x drill diameter.

Regards, Gary Wooding


#13

I just discovered all the responses to my drilling question. Thank
you all for taking the time to respond. I have alot of things to try.

I wasn’t lubricating consistantly. using a nail as a tool to start
the hole, using the correct drill bits–but not the best
quality.,etc.

How do you sharpen a drill bit? If I have been overheating the bits,
will they be fixable?

Again, thank you!
Jamie Tuohy


#14

The drill must produce swarf (chips or spirals of metal) while
drilling. If no swarf is forthcoming then something is wrong.

The first thing to try is more pressure. If cutting does not happen
with more pressure then the drill bit is blunt. A blunt drill will
rub the metal and work harden it, so try the harder pressure once
only and if it doesn’t cut then get your 3x or 10x magnifier and look
at the cutting edges of the drill bit.

I sharpen small jewellers drill bits freehand using the side of a
cutting disk in the flex shaft (and the bench grinder on any other
drill bit over 2mm). Just try to make the cutting edges of the drill
look the same as a new drill. With practise it will only take
one-second grind for each cutter against the abrasive disk. It is
easy once you learn how to orientate the drill bit and abrasive disk.
The important thing is there must be a clearance angle, and the two
cutting edges must be equal. Do a Google search on how to sharpen a
twist drill, or look up a basic metalwork text book to see the
correct names for the angles.

Broken drill bits that have been re-sharpened are shorter and can
withstand more abuse and higher pressure. There is a ‘but’ here; on
many drill bits the spiral flutes get shallower towards the top, so
the cutting edges on shortened drills may be smaller and the web
bigger. The web is the centre portion of the drill that does no
cutting, it has to mash through the metal, and it is the reason why
pressure is necessary. So a thicker web means you need more pressure,
and the shorter drill will withstand the extra pressure. Metalwork
textbooks explain how to grind the web thinner, again with practise
just a quick touch with the abrasive disk

You may find a quirk with small drill bits; they can ‘untwist’ if
they get too hot. That is, the spiral flutes become straight or even
reversed near the end. When this happens there is no rake angle and
it cannot cut even when sharpened. Cut off the straightened part (it
will usually be a grey or purple colour) and re-sharpen where the
twisted flutes are normal.

Alastair


#15

Hi James,

Small drill bits need really high speeds to cut correctly. The
recommended speed for a #60 drill bit in copper is 10,000-20,000
RPM (100-200 Surface Feet per Minute). 

These speeds are, in general, theoretical only (high speeds are
desirable for small carbide drills in shallow holes) and do not work
well in practice. Where are the figures from - they are usually from
nomograms published by drill manufacturers which extrapolate from a
generalised formula based on linear cutting speed. But which part of
the drill does this speed relate to? By using the formula, only the
extreme outer edge of the drill will run at this speed and, as with
all other drills, the cutting speed at the very centre will be zero

  • yet it still cuts OK ???!!

To use small drills at such high speeds it is necessary for the work
to be firmly fixed down and the drill to be held in a rigidly
supported and true running spindle, otherwise, the slightest flexing
or sideways movement will cause the drill to grab and break,
particularly in ‘sticky’ metals like copper and silver. Over the
years I have drilled many thousands of tiny, deep holes in brass (-
down to 0.1mm or 4 thou. diameter and 8 diameters depth ) and I get
the best results from using a spindle speed of just hundreds of RPM,
not tens of thousands. At these lower speeds, you can more easily
monitor the way the drill is cutting and adjust the pressure on it
before the drill bit snaps. It is most important that the drill cu=
ts continuously without skidding or digging in and that the chips
clear away steadily.

These high cutting speeds also assume that you are using an effective
coolant as, at 100 ft/min surface speed, the cutting edges will
rapidly heat, soften and dull. Where small drills are made to cut
more than about 1/2 or 2/3 their diameter depth, it is impossible to
get effective cooling as the gas bubbles coming off the boiling
liquid prevent further coolant entering the holes - on really tiny
holes, surface tension prevents the liquid getting in there to start
with. As the cutting edge dulls, you will feel that the cutting is
slowing down, apply more pressure to compensate, and, hey presto,
the drill breaks… Now you have to find somewhere that still
sells alum to dissolve the broken drill out of the hole and the job
has to sit for a few days before you can continue - not to mention
having to redesign a bit to cover up the ding that the drill made in
the side of the hole as it broke… Been there, done that, learned
the hard way… :frowning: but don’t do it any more…

Best wishes,

Ian
Ian W. Wright
Sheffield UK


#16

If you’re using small size drills it’s unlikely you’ll be able to
resharpen. Companies like Rio Grande sell high speed steel drills.

If you’re serious and can afford it the best solution is the drill
press. Foredom’s DP is well made. The use of a drill press will
greatly improve your situation.

Also using lubricant will prolong the life of your drills. You don’t
need to lubricate constantly; just each time you drill a hole.

If I drill, say a #67, I first center punch where I want to drill,
critical, and then using a toothpick place a drop of lubricant in
the mark and drill coming down slowly to the piece. I also us a piece
of wood to back the metal to be drilled; it’ll save wear and tear on
the drill.

KPK


#17

it is difficult to sharpen drills around 1-2 mm, you get a little
pamphlet or look in a machinist manual and read the drill sharpening
section, you need magnification(optivisor), it can be done well
with a separating disc on a flex but it must be even, and some of
the web must come out, it can also be done with a drilldr., but
you must still remove some web with a disc, practicing by copying
the exact profile that you see on a new drill will get you farther
than you might imagine

dp


#18

For copper you want a zero rake or a slightly negative rake on the
drill. a drill will normally have a positive rake which is a small
sharp appearing angle at the cutting edge. a zero rake looks like a
blunted edge or a 90 degree angle. a negative rake is a larger angle
than 90 degrees - a back slope. I know this may be counterintuitive
but it is right! on a number 60 drill it won’t take much with a hard
stone or diamond file to reshape the cutting edge. a split point
drill also will help but You may have trouble finding these in a # 60
or smaller.


#19

Ian,

These speeds are for high speed steel drills not carbide. I drill sub
millimeter holes regularly at 10,000 rpm using a fairly cheap $200
drill press purchased from Micro Mark made for tiny drills, certainly
not the highest quality spindle or bearings but it works. I will not
say I never break a bit but it is a very very rare occurrence. I hand
hold the work under the spindle resting on the table. I often am
going 8 to 10 diameters deep. I also drill freehand with a flexshaft
and use lower speeds. So while I agree you can cut successfully at
lower speeds I also know that the drill cuts best when the correct
SFM is used, when you go slow you are overloading the drills cutting
edge and more likely to have too large a chip which leads to broken
bits. At any speed the user needs to have more skill when using small
bits.

Jim

James Binnion
@James_Binnion
James Binnion Metal Arts


360-756-6550


#20
I get the best results from using a spindle speed of just hundreds
of RPM, not tens of thousands.

I totally agree. Low rpms, relieving pressure frequently and a
lubricant (I use wax) are the efficient way to use drills and burrs
for me. The cutting edge needs time to cut the metal and discard it.
Also you generate less heat. Generally it is no problem if the metal
heats up but high heat is very distructive for drills and burrs.

Lois
www.loismartens.com