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Twist drills wearing out after two uses


#1

My drill bits become dull after a few uses and I am interested in
people weighing in on which bits they have found hold their edge the
longest. I have been using high speed steel rather than tungsten,
vanadium or other types of coating as they are more expensive I
don’t know if they are any more effective. I would spend more if I
thought it would be worth it.

I use a flex shaft, make a divot with a center punch, and start with
a smaller hole before proceeding with larger bit. I also use bur
lubricant, allow the tool to do the work, drill on my wood bench
pin. (I don’t think misuse of tools is the issue).

I know a lot of people resharpen their bits I’m not interested in
doing that at this time. I am drilling in 18G brass so I know that
will make them wear out faster than silver or gold. I have looked at
an earlier thread in this forum which mentions a sharpening tool but
no one found it to be very effective.

Alternately, if anyone has a link to a helpful guide that would be
appreciated.


#2

Hi Mary,

Check your speed. The odds are pretty good that you’re over-spinning
the drills and the excess heat’s annealing the tip. Then they die.

I do a lot of production (CNC) drilling in steel with small (#49, or
.073") drills. We get thousands of cycles with pretty generic
drills, going about 3/16" deep in steel. We do use titanium nitride
coated (gold) drills, but those classify as generic these days.

Even with basic drills, you should be getting more than two holes.
With teeny drills, you really want shockingly high speeds, by
drillpress standards. (+4K RPM) but that’s not all that fast by
flex-shaft standards. (15K) So try it with the flex shaft ticking
over at about 1/4 speed, and see how that works. Also, try
lubricant, like burr-life or something. The goal is to keep the heat
down so it doesn’t fry your bits. (Brass is actually pretty easy to
drill, by comparison with most metals.)

It is worth paying the money for decent bits. For a while, I was
using 1/16" bits that cost $30 each, and was more than happy to pay
it. They let me double my cutting speed, and extended tool life by
30%. That won’t apply to hand drilling, but good drills save money
in the long run by making accurate holes, quickly.

FWIW,
Brian


#3

problem is twist drills being so small, even made of solid carbide,
used with lubricants, titanium nitride, or cobalt etc., coatings
simply wear out fast, no matter how soft the metal. Presuming you are
annealing your 18 g.

brass I would expect maybe 6 uses out of each bit- one reason
they’re sold in pkgs. of 6-12 by most vendors.

The main thing to remember, particularly with HSS is to use them
between 5,000 and max. of 10,000 in most flexshafts. Karl Fischer
sells some for hard metals

http://www.ganoksin.com/gnkurl/ep806z

Busch makes some too sold both individually and by the 10 pc/ pkg.
which I like when using an ordinary twist drill without an adapter
(water or lubricant set-up for diamond drills) for flexshaft use. in
a drill press I use Eureka brand twist drills with a TiN coating-
also sold by Fischer in Germany. However for a cheap alternative
Harbour freight sells a “grab set” of micro drills and rasps made of
carbide, that are generally resharpened but great quality for the
money and really fine(small) sizes. They do a world of things the
expensive drills do (as good as the diamond coated drills. pearl
drills, etc.) the thing is to check each package to make sure you get
bits in sizes and styles you can use. As for resharpening
micro-rasps, twist drills yourself- to me, it’s not worth the time
or end result and if “over done” can easily loose their temper,
becoming useless and more brittle. Besides the micro-rasps, HF sells
a 'grab bag" of 30 twist drills- but you have to open the pkg. to
check for the sizes as well as left or right handed orientation- you
could end up with 5 of 30 right handed bits. so it would have been
more practical to buy one 8.00 Eureka or Busch bit(s) in the size(s)
you need. Great for practising on. Again, as with any rotary tool,
flex shaft pendant motor, etc. the rotation of the tool not pressure
is the key to a successful drilling job on metal without a drill
press. Lubrication is essential- the liquids are probably better than
solids by a small margin. Even though you sound like you’re just
learning, this is one consumable in the studio that I would have to
say buy the best you can get-if working on precious metals, or metals
that aren’t going to receive some surface treatment after drilling (a
matte finish, patina, etc. as they can hide a ‘skip’ if the drill
gets away from you).Busch has dual cutting heads/surfaces on their
twist drills, so the metal is discharged and doesn’t load up the bit
causing overheating, skipping, etc. A diamond coated twist drill will
tend to grab onto the metal but again, the slower speed will greatly
improve their longevity, which is not all that long under the best
circumstances. being like small thin wires they simply love to break!
So ther are alternative cheap remedies and expensive brands to choose
from. If I were starting out I’d buy a couple of good drills in the
sizes you use most often, and a set of the HF micro-bits (after
checking the contents for drills as opposed to mostly rasps, or super
-micro sizes that won’t work for your purposes anyway) and see with
which you get the longest life Anneal your metal, lubricate the bit,
continue to make your divot with the smallest punch you have or can
make, and don’t let your tool run at max.-keep it between
5,000-10,000 rpm… rer


#4

HSS drills should do at least 50 holes before they need
resharpening.

We need to know from you

  1. drill sizes
  2. brass spec ie free machining 60/40 or 70/30
    speed of the 1st drill
    speed of the second drill.

Drills for brass need a steeper rake back that drills for steel.

Thats the angle from the cutting edge to the back of the drill land
as different from the included angle of the 2 cutting faces…

A small drill press is better than a dremel.

If youve hundreds of holes to drill consider using a Roper Whitney
hand tool and punch them through.

The 1/16th in rivet holes I need to hold the buckle fronts to the
buckle backs I make are all drilled using a small hand turned drill
press.

there are 4 holes through each component. They need to be accurate
and fast.

the drills last at least 100 holes before I need to sharpen them.

I do this with a small fine grit 2in dia grinding wheel run in a
dremel equivalent.

Hold the drill in one hand and the grinder in the other.

They rarely wear out, generally get broken first!.

Hope this helps.


#5

Hi Mary,

This may be a silly question, but are you running your flexi in the
right direction? Had a trick played on me when I left my bench, some
wise acre switched on the reverse. I was able to drill holes, but
for the life of me it was really hard work. Figured it out, had a
laugh :smiley:

Just use the tip of a scribe to make your starting point. Use lube
and try again.

Regards Charles A.


#6
I know a lot of people resharpen their bits I'm not interested in
doing that at this time. 

I see that you’re not interested, but I think sharpening is the best
solution and maybe others will be interested. All it takes is a
little practice. You can use a separating disc in your flex shaft and
just cut the two faces of the dull drill to the same angles as a new
drill, or as close as you can. Just look at it under magnification.
It’s not quite the same as a new drill because the cutting surface on
a new drill is actually curved slightly. But I always sharpen mine
and they work well and last a very long time that way.

As far as favorites, I like Busch, tungsten vanadium steel drills
with the 3/32 shank for use in quick release hand pieces.

Mark


#7

If you are not re-sharpening your bits you’re throwing money away.

Sharpening a drill bit is pretty much like sharpening a graver. You
learn the necessary angles and after a bit of practice your arm and
hand become accustomed to maintaining those angles during honing.

Bits smaller than 3mm don’t require a jig or appliance to
re-sharpen, you just have to practice at maintaining the correct
angle. Over 3mm it is more difficult as the length of the cutting
edges means that even small errors become magnified. But as you can
see from this table, there’s a bit of leeway on the angles.

When drilling soft metals the difference in hardness between
hardened steel and gold, silver, and copper is so great that you
don’t have to worry too much about maintaining perfect, optimum
angles; as long as it’s sharp it will cut. Drilling steel, or other
hard metals, is a different matter. There a sharpening jig is pretty
much necessary.


#8

I do use a lubricant and thought I was not drilling too fast but
will try slower. I don’t have the dial to control my speed, but I
have been putting my foot on the pedal with minimum pressure, as I
was always told to let the tool do the work.

Is there any brand of bits you recommend (don’t know if you can tell
me in this forum)?

Thanks also Mark. I do’t have a problem with my drill tip spinning
because I make a divot first. I have been considering a drill press.
It’s next on my list.


#9

Hi Mary,

A drill press (micro type) is definitely the most important thing
for small drills. What blows them up more often than anything else
is eccentricity. They’re so thin that if you get the handpiece the
least bit out of line with the hole, they snap. Drill presses keep
that from happening. Almost any little drill press is better than
nothing. If you were looking for somewhere to start, take a look at
the Proxxon mini drillpress, or the Foredom drill press attachment
for the flex-shaft. I’ve got the fancy one of those (DP-95) and am
quite happy with it. I do keep a spare #30 handpiece permanently
bolted into it, to save fussing with the bolts. (After you get to a
certain point in your metals life, you will have spare #30
handpieces floating around. They’re sort of like coathangers, but
they don’t breed quite as quickly.)

I normally get my drills from MSC (www.mscdirect.com) The important
thing is to get ‘screw machine’ length. They’re shorter than
standard ‘jobbers’ drills. Since we’re only going through a few MM
of stock at most, we don’t need all the length of a standard drill.
The shorter ones are stiffer than the full length ones, and thus
harder to break. (Go to mscdirect, and search for “Screw Machine
Length Drill” That’ll get you to a page that lets you select
diameter and manufacturer. Most of them are serious industrial
drills, but they’ll almost all be OK. Don’t buy Interstate, I’ve had
spectacularly bad luck with them, but the generic “made in USA” ones
are fine. Chicago-Latrobe is also very good. The gold titanium
nitride ones are classified “TiN” when it comes to the type of
coating. I just checked a.055" drill, (roughly 18Ga) and they were
running $3.41 ea, (Min 12) If you find one that you need, with a
stunning price, keep fishing for the same drill from a different
manufacturer. Some of the brands they carry are serious drills,
for situations you just can’t generate with manual equipment. The
’extras’ won’t do you any good, so there’s no point in paying for
them. (Those $30 1/16" drills were MA Ford 3 flute screw machine
drills from MSC. Weird, but incredibly useful.) (Useful in a CNC.
Pointless overkill by hand.)

I get a lot of my more ‘industrial’ supplies from MSC, they’re a
good place to know about. Not always the cheapest, but they’ll have
almost anything you might need. Think of them as the RioGrande of
the machine tool biz.

FWIW,
Brian


#10

In first year this was a conversation while the teacher was
demonstrating drilling, he was quizzing us:-

Teacher:  What speed should you drill metal at?
Me:  Depends on the alloy?
Teacher:  Okay, non-ferrous metals.
Me:  Fast.
Teacher: As fast as practical.

Regards Charles A.


#11

I like Busch brand bits for most operations - 2 cutting heads, and
self clean-out feature also Fischer in Germany sells a line for hard
metals and then there are dental lab intended diamond burs that are
sintered, pricey but last quite long when well maintained… Busch’s
are perhaps the most universally available quality burs sold by
vendors… rer


#12

Many tools come to us improperly, or not fully, finished… I
discovered that sharpening a bit myself gives a much better cut than
the way the drill comes, especially after it has been used for a long
time. It really is worth while learning to sharpen your drills, as it
only takes a second and saves a great deal of money. The trick is to
use a new, really large drill (say 1/2") as your model, so you can
very easily and clearly see the angles.

Janet in Jerusalem


#13

Bees wax works great as a lubricant. been using it for years. I
still use the same bits I have used for years without any problems.
I have a gross of each small size. Rotate them. They are cheap when
bought by the gross. so donot worry when I need to toss one. Figure
this into my cost of doing business.


#14
I like Busch brand bits for most operations - 2 cutting heads, and
self clean-out feature also Fischer in Germany sells a line for
hard metals and then there are dental lab intended diamond burs
that are sintered, pricey but last quite long when well maintained.
Busch's are perhaps the most universally available quality burs
sold by vendors. rer 

Busch have steel, high speed steel and carbide drill bits. You can
tell from a distance the carbide drill bits, because there’s only two
in a pack as opposed to the six drills in the other varieties.

Found out the other day that Valorbe has a premium range of saw
blades Granit, I’m trying to convince my boss to import the range.

So many products and brands to find out about :slight_smile:

Regards Charles A.


#15
Many tools come to us improperly, or not fully, finished.... I
discovered that sharpening a bit myself gives a much better cut
than the way the drill comes, especially after it has been used for
a long time. 

Many tools that we are using are not intended for goldsmith work.
They are adopted from other fields and often sold as is. It is up to
a goldsmith to make them useful.

Drills are sharpened to be effective for drilling carbon steel in
annealed state. They must be re-sharpened for goldsmith work right
from the start, to insure long use. What is long use ? At least a
hundred drillings per single sharpening. I am sorry, but I cannot
give any recommendations on which drills to buy. Many years ago, I
have purchased a few dozens from aircraft manufacture on Long Island
(the name escapes me at the moment), and I am still using them. I
guess, look for aircraft quality drills. I have tried modern types,
which do not require chuck, and I do not like them.

Factors affecting drill life are numerous and cannot be pin-pointed
to a single factor.

That said, a lot of recommendation given on this subject are good
for carbon steel work, but not for goldsmithing. Using drill press is
not a substitute for good drilling technique. For a lot of situations
drill press is useless.

Speed of drilling by itself is a meaningless term. Drilling envelope
composed of speed and pressure (feed), which should be considered
together. At the start of drilling, pressure should be moderate and
speed should be low. (Terms like moderate, low, high, - are in
relation to average values for a particular metal) As depth is
increasing, speed should be increasing as well with pressure been
eased up. At the exit, pressure should be almost non-existant with
speed at it’s highest. The best indicator of pressure/speed been in
proper range is well formed swarf.

I disagree with recommendation of using short length drills. They
may be better for drill presses because of minimized chance of
deflection at the start, but for hand-drilling long drills are
better. The longer the drill, the more it can absorb of
irregularities. I also recommend not to over-tighten chuck holding
drill. It is a common mistake leading to premature drill failure.

There are so much more can be said here, so it probably deserves a
blog entry. May be I will do one. Incidentally, the tutorial I have
promised before leaving for Rome on square setting construction has
been published under Design 3.

Any questions in regards to it, use comments at the blog, so other
readers can benefit from answers.

Leonid Surpin
Studioarete.com


#16

Hi Leonid,

You knew I was going to have to reply, didn’t you?

Drills are sharpened to be effective for drilling carbon steel in
annealed state. They must be re-sharpened for goldsmith work right
from the start, to insure long use. What is long use ? 

Not exactly. Depending on the drill, they could be intended for
anything from soft non-ferris metals (like gold) to hardened steel.
Just depends on what drill you order. Most ‘generic’ drills have a
sort of general grind on them that will work just fine in many
different situations, so long as you don’t push them to the edge of
their envelope the way you do in production.

Now that we’re doing the saw parts in a different machine, we don’t
need to blow a 1/16" hole through half an inch of steel, so I’ve
backed off the expensive drills. Now, I’m using the same basic 1/16
drill on both the steel parts and the aluminum ones. I get thousands
of cycles in either material, with the same very basic drill.
(Chicago Latrobe, 1/16" TiN, screw machine length. 118=CB=9A split
point.) I’d reach for that same drill in silver or gold.Come to
think, I’ve used them in brass, and gotten a few thousand parts per
drill in brass too. I think I’d call that long use.

What I can tell you for sure is that quality drills are as good as
they’re ever going to be, straight out of the box. (The cheapo
import ones? Probably also as good as they’ll ever be, but that’s a
rather low bar.)

The guy in the next bay over from us is a tool & cutter grinder. He
makes his living resharpening drills and cutters, and he’s damned
good at it. I’ve chatted with him about the zen of re-sharpening,
and it’s surprising how critical the angles are, especially on small
bits. You may be able to wing it well enough to ‘save’ a dull bit,
at least enough for a few more holes, but there’s no way to get the
angles as perfect as they have to be, by hand. When he’s re-grinding
small bits, he’s using a multi thousand dollar machine, looking
through a microscope to get the grind right.

It should tell you something that the ‘right’ geometry is critical
enough to support an entire shop that does nothing but re-sharpen
cutters right.

To be blunt, goldsmithing applications usually aren’t all that
critical, so ‘close enough’ is probably OK. But there’s no reason to
trash a perfectly good drill by butchering the tip unused, just
’cause. Yes, once upon a time, many drills were poorly ground, out
of the box. But that was long ago and far away. The modern quality
ones are very good indeed. This isn’t to say that you can’t resharpen
bits by hand in a pinch. Lord knows I’ve done it enough, on bits
from a few thousandths wide all the way up to more than an inch, but
it’s not my first choice, and I don’t do it unless I have to, or on
anything where the hole quality is critical. It also means that I
replace the resharpened drill as soon as possible.

which do not require chuck, and I do not like them. 

“Which do not require chuck"e OK, how does one hold onto them
without a chuck? You mean the ones with the 1/8” solid shank, for
grabbing in a collet handpiece? My memory is that those are normally
solid carbide, and thus brittle as hell. Not something I’d ever
consider using by hand, normally. I think those were originally
intended for CNC drilling of circuit boards. (which are fiberglass,
and thus so abrasive that they destroy normal drills pretty
quickly.) Just because a jewelry supplier is selling it, does not
mean it was originally (or ever) intended for what we’re using it
for.

That said, a lot of recommendation given on this subject are good
for carbon steel work, but not for goldsmithing. Using drill press
is not a substitute for good drilling technique. For a lot of
situations drill press is useless. 

How do you figure? Proper support, and perfect concentricity are
useless how?

Speed of drilling by itself is a meaningless term. Drilling
envelope composed of speed and pressure (feed), which should be
considered 

The way it’s actually calculated is ‘cut per tooth’ which is a
factor of the number of teeth (generally 2) combined with the speed
of rotation (RPM) and the advance per revolution.

You can find all sorts of calculators for it online. One is here:
http://www.ganoksin.com/gnkurl/ep807i

The short form is that you consult your charts to figure out what
the recommended SFM (surface feet/minute) rate for a given
combination of material and drillbit is, and then work back from
that combined with your drill diameter to figure out the spindle RPM
and maximum cut per revolution.

(One way to spot a quality drill is to check to see if the
manufacturer has a website where you can look up the recommended
speeds & feeds for their particular drills. They’re not all the
same.) Working it out mathematically is how you get thousands of
parts per drill. For hand goldsmithing, most of this is wild,
unbelievable, overkill, but it is perhaps useful to know about.

The reason you have to slow down as the bit exits the back of the
piece is because you don’t have it in a drillpress. The flutes grab
that last little bit of metal at the edges of the hole, and torque
the bit. If the drill is hand-held, it’ll snap. Properly clamped in
a decent drillpress? No problem.

I disagree with recommendation of using short length drills. They
may be better for drill presses because of minimized chance of
deflection at the start, but for hand-drilling long drills are
better. The longer the drill, the more it can absorb of
irregularities. I also recommend not to over-tighten chuck holding
drill. It is a common mistake leading to premature drill failure. 

Clearly, we’ll have to disagree on this one. The short drills are
actually better for hand drilling because they don’t flex. I can
use long ones in a drill press with no problem, because the drill
press holds the drill concentric, so it doesn’t matter how flexible
it may be, because it can’t.

For hand drilling, there shouldn’t be any irregularities, at all.
Ever. Irregularities are what break bits. Having a flexible bit just
lets the irregularities get out of control. I would have thought you
of all people would detest triangular and oval holes.

irregularities. I also recommend not to over-tighten chuck holding
drill. It is a common mistake leading to premature drill failure. 

e? How do you figuree Given that I tend to tighten mine in a vise,
with a wrench, I’m most curious about why tight is bad.

Regards,
Brian


#17

I was thinking of this thread today as I started a job. I
deliberately picked an older 0.77mm plain Stuller high speed drill
bit that I had resharpened using a snap-on disc, with only one
cutting face cut on each side. I drilled 24 holes in 20 ga 14K white
sheet with just this one bit.

By the last hole the bit was starting to need resharpening, but it
was still cutting fairly well.

I hold the flex shaft in my left hand, and my left thumb acts as my
drillpress, controlling depth, angle and pressure. Under
magnification I focus on keeping the speed and pressure just fast
enough to cut a continual flow of chips or chaff, and I re-lube the
drill bit with Bur-life after every cut. Never cut so fast that the
bur-life smokes, or the bit will be history.

I will keep resharpening a bit as long is any fluting remains on the
drill shank, and a small package of drill bits (10 drills I think)
will usuallylast me a couple of years, unless I get into a really
big, heavy thickjob where I do tend to get impatient, and I push to
quickly, breaking or burning the bits out.


#18

Twist drills wearing out after two uses

Many tools that we are using are not intended for goldsmith work.
They are adopted from other fields and often sold as is. It is up
to a goldsmith to make them useful. 

As regards brands and types, this comment has reminded me of the
fact that my drills are dental drills (Busch). I think that dental
equipment is often/usually well-geared to goldsmiths’ work. I’ve
been using the same one pkg.-of-6 (per size) for many years now that
I grind my own points.

Janet in Jerusalem


#19
Clearly, we'll have to disagree on this one. The short drills are
actually better for hand drilling because they *don't* flex. 

You have made a lot of points, which demonstrate difference in
approach to drilling. Points are not wrong. They simply not very
useful for someone who has to drill by hand. Length of drill bit is
such a demarcation line. I am using long drills precisely due to
their flexibility. Flexibility make them survive in situations where
short bit will snap.

Sharpening is another point. I am fully cognizant of importance of
sharpening angles, but I am limited to what I have on hand. Equipment
to produce precisely sharpened bits is not what commonly found in
goldsmith’s shop. My view on drilling technique is that one has to
adopt industrial methods to primitive environment of goldsmith
bench. That is all I am saying.

Leonid Surpin
Studioarete.com


#20

Larger drill bits, I regrind the dull/broken ones with a cut-off
disk. Since I am frequently in a school environment and often have
piles of drill bits left behind from students. Not necessarily my
students but from other classes, so not to waste time getting new
drill bits, I do resharping and general maintenance. I do find the
really small drill bits not worth resharpening but #60 and lower are
fine. again, I’m always yelling at my students to use the damn Bur
Life every time they drill. I am a slave to my own Lube Stick or Bur
Life. I find I end up doing a lot of corrective maintenance to the 2
studios I teach at - one, nobody takes care of it and the other, the
Guild members needs to be reminded frequently. I’m glad I have my own
workshop that everything functions the way its supposed to. Joy