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Cause of an handpiece accident?


#1

Today I was preparing a new graver. (Nope, it wasn’t a graver
accident). After mounting the handle, I used a heatless mizzy wheel
on a reinforced shank in my Foredom #30 handpiece (with Foredom SR
motor), to grind and shape the spine of the graver. I was taking my
time, just filling time between appointments (ie slow and throughtful

  • no rush). I was running themotor at about half speed (or perhaps
    less) and dipping the graver in cold water frequently to disperse the
    heat. The handpiece was in my right hand and the graver was in my
    left hand, resting on the bench. Suddenly, the reinforced steel shank
    with the mizzy was bent about 70 degrees, just where the shank enters
    the chuck of the handpiece… It didn’t break, it just bent.

There was nothing nearby for the mizzy to “catch” on (no long
sleeves, fabric, strings, hair, etc.) Nothing was out of place on the
bench when the episode was over. The graver that I was working on
remained in my left hand, on the bench. I thought that there might be
a defect in the shank of the mizzy that allowed it to bend with
lateral pressure. But I’ve examined the bent shank of the mizzy and
can’t see any obvious shank defects Also, there was no undue lateral
pressure on the mizzy/shank (I’m not that strong)

The bent mizzy/shank hit the fingernail bed of my right forefinger &
I ended up with a nasty hematoma under the nail, but no sprain,
fracture or other injury. It’s still throbbing several hours later,
but I’m counting myself as LUCKY, since it could have been so much
worse

So… this is where I’m asking for your collective wisdom. I’m
nervous about picking up the handpiece again without diagnosing the
causeof this accident. Has this ever happened to you? Do you have an
idea regarding the cause? Thanks for your help!

Jamie


#2

I have bent my share of shanks. Memory suggests that I was using a
fairly heavy medium such a mizzy wheel when a slight bend in the
shank threw it out if balance and caused the centrifugal force to
throw it way out of balance. Perhaps you just caused a slight bend
in the shank while it was turning.

Bruce Holmgrain
JACMBJ


#3

Hi Jamie:

I had a student do something similar once upon a time. Near as we
could figure, he got the shank of the tool caught between two out of
the three jaws of the jacobs chuck. That’ll hold it enough to spin
it, and even do some very light work, (so long as you don’t mind (or
notice) the eccentricity (or thumping.)

But as soon as you put any real pressure on it, it’ll pop loose.
Depending on what happens next, it can get fairly dramatically angled
before it slides itself back between two of the jaw teeth. They then
proceed to grab the shank at whatever extreme angle it managed to get
itself to, and whirl it around. Usually slamming it into something
(like your finger) which proceeds to bend the shank.

This isn’t as hard to do as you’d think, and depending on how you
did it, the working head of the mizzy might have been more-or-less
centered. So the thumping wouldn’t have been very great. Not any
worse than mizzies sometimes have anyway if you mount a new wheel on
the mandrel. I’ve done it once or twice when I was in a hurry, and
changing over from a large shank to a small one, or if I’d really
opened up the jaws for some reason. (you mention that you’re using a
thick mandrel…) Now, I’m paranoid enough that I usually eyeball the
chuck once, just out of habit, to prevent such entertainment.

Of course, if you’re using a collet handpiece, this can’t happen, so
just ignore the foregoing.

Regards,
Brian.


#4
So...... this is where I'm asking for your collective wisdom. I'm
nervous about picking up the handpiece again without diagnosing
the causeof this accident. Has this ever happened to you? Do you
have an idea regarding the cause? Thanks for your help! 

It’s not likely the handpiece, though you should put a small tipped
bur in and make sure it spins reasonably true, without too much
wobble. Mizzy’s, especially the larger ones, are somewhat heavier
than some things we might mount on a mandrel, so if it jumps even a
bit, with vibration or whatever, it might be then running not true
with the combined rotational motion and whatever bump to the
handpiece. Or perhaps it really just is a bad mandrel. Most of them
are soft steel, not hardened. Some are even just brass. I’ve had them
bend on me too, now and then. Sometimes the apparent cause is having
the mandrel not fully inserted down into the chuck, so too much of it
extends forward of the chuck. Occasionally, a #30 chuck can, under
vibration, work a bit loose, so the mandrel is no longer tightly
gripped. If that happens, having it go awry is much more likely. All
in all, I’d chalk it up to remembering to make sure the mandrel isn’t
a little bent to begin with, to make sure attachments are running
true without vibration, and to make sure they’re fully inserted in
the chuck with the chuck fully tightened.

And as an ancillary note, things like this are part of why one
always should be wearing eye protection.

Peter


#5
It has happened with the softer nickel or chrome plated (some sort
of metal shank) lower cost shanks. I now only use stainless steel
shanks and I don't have any problem. The cost difference is not
that much either. 

To stop the pain of the damaged nail bed, drill a hole in the nail
over the blood spot to relive the pressure. Sounds terrible but the
pain will be relieved. Use either the flex shaft to drive the drill
or you can use a pin vise or just your fingers to twist the drill.
If these don’t sound dooable, use a new pointy hobby knife blade to
make the hole. This hole may be so small that blood clots and closes
the hole that much be opened again. Lastly, a very hot (heated in the
burner flame) paperclip wire can be used to burn a hole into the
nail (this method is often used by doctors).

Good luck with both your finger and bending shafts.
John Dach


#6
The bent mizzy/shank hit the fingernail bed of my right forefinger
& I ended up with a nasty hematoma under the nail 

This has happened to me before, too. I trim my mizzy or sanding
shaft to just above the end of my hand piece so there is less
material to bend…

This leads me to a question. Does anyone know who supplies steel
mizzy and sanding mandrels? The nickle plated brass ones are forever
bending out of true. I would very much like to buy some very good
quality ones.

Cheers,
Hans Meevis


#7

Dear Jamie,

I can’t answer your question about the handpiece, but if you go to
the ER or perhaps your family MD, he/she can quickly relieve the
pressure under that nail.

Lorraine


#8

Try Rio Grande for stainless shafts.

John Dach


#9

Hope you got the hematoma relieved. If it is still hurting, you need
to let the pressure out. You can figure how to do this as I don’t
want to give you medical advice over the internet, but a hot
paperclip can melt a hole in the fingernail, but you have to be real
careful to not go into the flesh under the hematoma. Of course if
you do this, the fingernail will fall off, but it will regrow
everntually.

John
John Atwell Rasmussen
Rasmussen Gems and Jewelry
Web: www.rasmussengems.com
Blog: http://rasmussengems.ganoksin.com/blogs/


#10

Rio Grande do stainless steel ones, the little screws are much
stronger too. Go for the ones with the flared shank.

regards Tim Blades.


#11

I would suggest using a small ball burr instead of a drill. Use the
side of the burr for cutting like you are trying to cut a groove in
the nail rather than coming straight down, that way when you do cut
through the nail there is little chance of driving it into your
finger. This method gives you much more control as you can just
gradually go deeper until you have penetrated the nail. Just did
this a couple of week ago on my big toe, worked like a charm.


#12
Hope you got the hematoma relieved. If it is still hurting, you
need to let the pressure out. 

After this length of time the blood will have clotted and the
pressure will The procedure is most effective during the initial
swelling while the blood is still liquid.

Pam Chott
www.songofthephoenix.com


#13

Put ice or ice pack over your injuried thumb right the way. It may
prevent inflammation. It works extremely well with burnt, sting too.

thomas


#14
To stop the pain of the damaged nail bed, drill a hole in the nail
over the blood spot to relive the pressure. a very hot (heated in
the burner flame) paperclip wire can be used to burn a hole into
the nail (this method is often used by doctors). 

Doctors use the heated-pin method because, in addition to burning a
small hole quickly through the nail without much pressure, it’s also
sterile

Please! Do not drill through your own fingernail with a drill! You
could end up with an infection that might require removing the entire
nail. The nail might not grow back, and that fingertip could be
painful forever without a nail to protect it.

Your fingers are your livelihood. Take good care of them.

Lorraine


#15
Doctors use the heated-pin method because, in addition to burning
a small hole quickly through the nail without much pressure, it's
also *sterile* 

There’s another reason-- when the hot wire penetrates the nail,
blood is released and it quenches the hot wire, making excessive
penetration unlikely. And of course, it takes pretty much no
pressure to work. But heat the wire in an alcohol lamp, not your
torch!

Noel


#16

Thanks to you all for your thoughts. I especially got a kick out of
the fact that there were more solutions to treating my injury than
the flexshaft accident cause. It just shows how ingenious all of the
Orchid members are (or maybe how many self-treated injuries they have
sustained). I think that my limit on self-surgery is superglue and
lacerations! Or perhaps since 24-hours had elapsed and the pain had
subsided by the time I received your suggestions, I was no longer
desperate for medical solutions.

Anyway, regarding the cause of the accident, I’ve been able to rule
out most of the suggestions and believe that the cause is related
to…

 Mizzy's are somewhat heavier than some things we might mount on a
mandrel, so if it jumps even a bit, with vibration or whatever, it
might be then running not true with the combined rotational motion
and whatever bump to the handpiece... 

I also found that the shank that bent was inch longer than most of
my other shanks (found one other longer shank in my drawer). Shanks
aren’t sold in multiple lengths, so the length must be a
manufacturer’s decision. The extra length may have exacerbated an
out-of-balance problem in my situation. I’ll pay more attention when
I purchase shanks in the future. Hans mentioned shortening the shank
length for heavier bits. I never thought about this before, but will
from now on. And John, thanks for the heads-up on the stainless-steel
shanks.

Here’s to an injury-free holiday season!
Jamie


#17
Hans mentioned shortening the shank length for heavier bits. I
never thought about this before, but will from now on. 

It’s that old principle of moments. The longer the distance from the
fulcrum (ie the longer the shank), the less force is needed to bend
it. Therefore, for a heavier bit (or any bit), a shorter shank will
mean it’s less likely to bend than a longer one.

Helen
UK


#18

Something that works great for internal bleeding, hematoma, abcess
under skin, etc… is Arnica. It is an herb, and used in
homeopathic treatment. It is an excellent treatment for anything
related to internal bruising, swelling or other tissue-trauma. I once
had a cat that had a horrible accident and suffered an internal
abcess on the side of her face the size of an orange! I treated her
with Arnica and within days it had shrunken to the size of a pea, and
was completely gone in a week. This wonderful medicine saved me
hundreds of dollars in vet bills. My dance instructor gets it in a
cream form to put on bruises, and wherever one may have pain from
pulled muscles or other dance related injuries.

Thought I’d share that :slight_smile:


#19

Hi Jamie,

It might be a little late for an answered, but here’s what happened.

You had the shank turning to fast for the strength of that shank. By
the way stainless steel shanks are even softer that carbon steel
shanks. There was a minute wobble that caused the mizzy wheel weight
to go exocentric. It continue till it hit the max compression of the
shank on one side.

Your finger acted as a brake.

Cure for this happening again. Shorten the shank or reduce the speed.
If your going to shape graver. Don’t use a mizzy wheel. Your working
to hard with the wrong tool. A bench grind will do the job, you have
to cool the blade more often in water. Even better is a lapidary
grinder so you can use water while your grinding.

There are even better methods on GRS site.

Jim
Jim Zimmerman
Alpine Custom Jewellers & Repair
http://www.handengravingcanada.com


#20

I have had the same accident - though not with such traumatic
consequences! I started a long time ago cutting off almost all of my
mandrels. Those which have the “swelling” into which the screw is
threaded, I cut off so that the swelling is touching the jaws of the
handpiece. Only occasionally will I leave a mandrel long for some
special reason.