Broken drill bit

Eventually it also happened to me. I broke a 0,7 mm drill in an
almost finished piece of sterling silver. Remembering the matter was
discussed here about two htree months ago I searched the archives. I
have now tried to boil the piece in alum with no reaction, same with
10 and 20 per cent hot sulphuric and hydrocloric acid. The drill is a
swiss Antilope mark, saying good for 30.000 RPM max, Acier PM. I’m
afraid the last means acid resistent, at least it seems to be.
Anybody out there got an idea? Any help would be highly appreciated.

Kind regards from cold, windy Denmark
Niels Lovschal, Jyllinge, Denmark

Hi: `Perhaps a formula called aqua regia would acomplish this as it
has nitric acid…just a suggestion…Ringman John

Try boiling the piece in a highly saturated solution of alum
(available at drug stores and groceries) on a hot plate for a couple
hours. Check it every 20 min. or so.

Andy cooperman

Hello Niels, Is it possible that you have some oil on the drill? Oil
could be protecting it from the acid. Make sure that it is clean and
then try it again. Another thing to try is Sparex II (Sodium
Bisulfate). Timothy A. Hansen

TAH Handcrafted Jewelry
E-Mail: @Timothy_A_Hansen

Acier means steel. Use a supersaturated solution of alum, it will
work, Charles

Charles Lewton-Brain
Box 1624, Ste M, Calgary, Alberta, T2P 2L7, Canada

ts probably solid tungsten carbide. EDM (electric discharge
machining) sounds the best (only?) way. Jesse

Niels, You may have already tried it, but if the item is not too thick
or your were close to getting through the other side, you can try to
punch the bit out from the opposite side. I sometimes use an old bur
that I can sharpen the end. Ken

Were you trying to drill all the way through the piece, or just part
way? Sorry I haven’t been following this particular thread and I don’t
know the particulars. There are techniques mechanics use for sheared
bolts using reverse drills and threads. Can you drill from the "back"
side and force out the bit, I think the direction of rotation would
reverse the broken bit? Will E.

Sounds like a high speed steel bit to me. Can you drill from the
other side and push it out with a punch? If not, you can ‘burn’ it out
by electrical discharge similar to EDM if you can rig up the equipment
or know anyone with an EDM machine- it’s how machinists remove broken
taps out of holes (which don’t ‘rust’ either).They burn them out, weld
up the hole if necessary, and re-drill the hole.

Niels, If it is a through hole, try drilling it out from the other
side with a slightly larger drill bit. You’ll ruin the bit but if it
is a last resort move… I’ve also managed to dig one out with a
scraper and once even punched enough of one out from the back with a
spring loaded center punch to remove it with pliers. Some of these
desperation moves only work if you have enough metal to remove to
minimize the unsightly gashes. Linda M

Hello Niels!

Forgive me for stating what you probably will find obvious. I
followed this thread awhile back too. I never approach a broken drill
chemically. I suppose the reason is: I can’t wait that long!

Do your level best to bur a small depression aligned with the drill.
Use a drill smaller than the broken one to drill perpendicular to the
broken one. When the drill dulls and you are in line with the broken
drill; make a drift punch out of an old bur shank, and punch or push
it out.

Assuming you can’t access the area, for the prior solution; here is
another idea. Bur the hole with a ball bur; carefully staying aligned
with the broken drill. Bend a drill by heating red hot and bending at
an angle. Form a suitable shape to reach the hole you have burred.
You could sharpen the end to cut if it will help. Put the bent drill
in a pair of pliers (parallel, chain nose, etc.) or pin vise. You may
be able to push it out. Drop a little oil in the broken drill hole.
Hope I haven’t wasted your time reasding this!

To remove a drill usually takes the time of setting several stones. It
is always a real pain. Good luck. Tim

Hydrochloric acid will dissolve iron and steel, almost any alloy.
You will get a white film of silver chloride on the piece, however,
and I’m not sure how easy this will be to get off.

Karl J. Kuhlmann

Boiling in saturated alum solution is fine, no damage to the metal.
But doing it in a container in the ultrasonic works conciderably

Etienne Perret
Designing Colored Diamond Jewels
< >
20 Main St
Camden, Maine
USA 04843

I would be extremely cautious about using aqua regia. It is full
reagent nitric and sulfuric acid. It is one of the 2 acids that
dissolve 24K gold. It eats up silver violently. Try some of the
alternative suggestions first. I have even back drilled the piece,
slowly and delicately, then driven the broken drill end with a fine
punch. Good luck!

Hi all, All of the pre mentioned options work, however let me add
another direction. Household clorox works brilliantly and will remove
that drill bit in approximately an hour. Gold items are a breeze but it
will darken the silver somewhat but a quick flame and pickle will
solve that. Steam the hole to clear any debris every 15-20 mins. Best
Neil George

Neil, I would not use bleach on any jewelry as it can cause stress
crack corrosion and things like prongs can fall off. You can also
get the same problem with ammonia. Stick to alum or sparex for drill
bit removal.


James Binnion Metal Arts
4701 San Leandro St #18
Oakland, CA 94601

   I would be extremely cautious about using aqua regia.  It is
full reagent nitric and sulfuric acid.  It is one of the 2 acids
that dissolve 24K gold.  It eats up silver violently.  Try some of
the alternative suggestions first.   I have even back drilled the
piece, slowly and delicately, then driven the broken drill end with
a fine punch 

Actually, Norman, aqua regia is nitric and Hydrochloric, not
sulphuric acid. And silver, depending on the acid, is not always
cleanly attacked. the silver forms a silver chloride film, which is
insoluable, and tends to protect the metal underneath. Not very
well, and with fresh a.r. it will still be attacked. but not as well
as is gold. And, you say it’s one of 2 acids that dissolve 24K…
What’s the other? I’m unaware of any other ACID formula that will
attack 24K… Cyanides attack it, but they aren’t acids…

Peter Rowe

Jim, Thank you for the reply. I have used this method to remove broken
drills for 20+ years without a problem, and I am really interested in
learning what the science behind your concern is. I am not a chemist
therefore any info on the subject will be well received. The fact is
you can teach an old dog new tricks with the right biscuit :-).

I would agree that a prolonged exposure would be detrimental, however
for the short duration of the process, it has never posed a problem. I
know that both Clorox and Ammonia are corrosive, but we are dealing
with noble metals are we not. The silver, yes darkens, the gold does
not…this is to be expected. Look forward to you correspondence. Neil

Hi Jim and Neil, Bleach does allot of stress and erosion on gold and
silver. Weakening the prong setting. I was talking to my pool guy
when I lived in Orange County in Ca. He told me he literally vacuumed
lots of diamonds from the bottoms of swimming pools in Resorts and
Homes. I guess that’s one of the perks of that business. For some
reason or another ladies just hate to take their jewelry off when swimming.
Susan Chastain

Selenium acid over 200 C will attack pure gold and cyanide itself
don`t attack to gold there has to be an oxidizer around, then it will
do. Teppo Niiranen