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Shocking experience with buffer


#1

Hello Orchidland,

My one complaint related to my buffing machine is the occasional
shock of static electricity I get. At least I think it’s static
electricity. After using the machine and turning it off, sometimes
I’ll get a zap when touching or getting close to the motor housing.
Its a sealed Baldor motor. The unit is about 15 years old and has not
been roughly used. Three-pronged plug is fully inserted to a power
strip, connected to a grounded outlet.

Any comments?? Suggestions??

Thanks everso,
Judy in Kansas


#2

Judy,

May I suggest grounding your machine a 2nd time from the unit to a
bolt; tbo it really shouldn’t do that ~ or use a grounding wrist
strap like this: http://www.outletpc.com/c0181.html

Cheers,
Ryan Taylor - Toronto
www.establishment.ca


#3

Hey Judy !

Static electricity shock is a real pain in the rear ! I have that
problem when I use the vertical belt sander when the weather is dry.
One way to solve the problem is to hold onto something which is
metallic with one hand while working the object with the other hand.
Another way to discharge the built up static electricity is to have a
metallic object in your hand and touch it to something else that is
metallic. I sometimes do this with a key when wearing clothing that
is prone to static generation. As I approach a door I will touch the
handle with my key. Static electricity can be a real dangerous thing
when there are volatiles in the work area.

Ron MIlls, Mills Gem Co. Los Osos, Ca.


#4

First and most important, I am not recommending that you use your
body as an electrical tester. However, there are some subjective
indicators you can glean from your experience. Sensations from static
electricity come from a high voltage spark between you and ground.
What you feel the heat, pressure from superheated expanding air, and
hear a pop. It produces a very small explosion near the surface of
the skin.

Small static charges differ from household electricity shocks in
that they produce the spark and don’t stimulate muscles to twitch. If
your household electricity current were strong enough to spark, pop
etc, you would be receiving the “shock of your lifetime” probably
strong enough to kill. Household current passes through the body
stimulating the nerves that control muscles causing muscles to
contract, vibrate, and twitch, hence the “jolt.”

Static charge is a much higher voltage but is built up on the
surface of your skin. When you get close to a grounded object it
produces the very small lightning bolt that does not actually pass
through your body. It can be more comfortably discharged by holding a
metal object in your hand, using it to touch something that is
grounded. The micro-explosive spark then initiates from the metal
object rather than the surface of the skin. (OK when you are sure
you are dealing with static, not a good idea to use to determine
whether it is static you are dealing with.)

So, the indications aRe: Static electricity will give a single
pop-zap, discharging the charge from your body, and be done. Static
will use any path to ground, even if it is not associated with the
motor. A shock from a faulty electrical connection would be a
tingling or jolt that occurs over a period of time while you are
touching the machine. If you touch the machine again, you may get
another shock.

If you are getting the jolt type shock, then you need to investigate
further. A three prong plug and receptacle is an indication of a good
path to ground but does not guarantee it. Hardware stores sell a
relatively inexpensive tester for testing the wiring of your
receptacle. If the receptacle is wired correctly, you need to check
to ensure that your main breaker box has what is called a grounding
electrode. It is a metal rod driven into the ground outside near your
electric meter. It will have a wire clamped to it that comes from
your breaker box.

If all of that is in order you need to ensure that the three prong
cord has the green wire properly attached to the metal casing of your
motor. Depending on the type, old motors can sometimes still give
small electrical shocks even when everything is properly grounded.
Many motors have carbon brushes (pads that conduct electricity to the
spinning part of the motor. The brushes can cast off dust that
provides a low grade path from the energized (hot) wire to the
casing.

If all of your grounding is proper, you can have a ground fault
interrupter receptacle installed that will prevent shocks from the
casing by tripping whenever the electricity takes a shortcut to
ground (like through the casing or through you). When it trips, it
shuts off the electricity supply to the motor. A frequently tripping
GFI would be an indication that your needs servicing. Worn motor
brushes can ruin the motor. A good motor repair shop will replace
brushes, turn armature, and clean out the dust from the brushes.

Howard Woods
Eagle, Idaho.


#5

Ground it with a copper wire to a water pipe.


#6

Judy,

Assuming the outlet and Polisher wiring is good then the problem is
you are building up a charge and will get a shock when ever you
touch a grounded device. I suggest getting a computer keyboard
discharge strip and affixing it near the buffer. Touch it for a
second to discharge yourself.

This assumes that the wiring on the polisher is truly good and it
really is grounded. If in doubt ask an electrician or anyone with a
voltmeter / ohmmeter to test both the outlet and the polishers
wiring as well as continuity from the motor housing to the ground pin
on the plug.

It happens more often than you would believe that outlets are
incorrectly wired. Another common error is to put a motor on a
rubber mounted anti vibration mount and not connect a grounding strap
from the motor to the metal case of the machine (or just use a solid
wire which breaks after a while from the vibration, there is a reason
grounding straps are made from a braid of fine wires with terminals
at both ends). The then connect the ground pin on the plug only to
the machine’s metal casing.

On the same subject most electrical supply houses (As well as Radio
shack / The Source stores in North America) have what looks like a
glorified plug with 3 indicator lights for testing outlets.

Kay


#7

Judy, before you turn that buffer on one more time have it checked,
you should NOT get a shock from the housing. There is an electric
motor service shop in most every city who can easily find the
electrical leak and it probably will not be expensive to find and
fix. Just check the yellow pages. It will probably be an old, dirty
and very industrial place, some of them are almost like a
Frankenstein Museum. Baldor motors are excellent and should last
nearly forever, but you have a potentially VERY SERIOUS situation.

Let us know when it’s fixed and you’re still alive.

Dr. Mac


#8

My work partner gets shocked all the time, but I don’t. Go figure.
He can buff or even touch the radio and get a shock. I think it’s
his shoes, or maybe he is just more charged than I am. Janine in
Redding with a shocking work partner, Gary. and yes he deserves
shocking. :slight_smile:


#9

Buffing can produce a static charge particularly in a dry winter
climate-- Kansas should qualify. Tie a ground wire from the motor
frame to your electrical ground or to a cold water pipe which might
be better if you have a GFI… If you are at the university ask a EE
for help.

Jesse


#10

One of our buffers was giving shocks. Electrical short tickles not
the quick static kind. Shocks occurred when changing buffs and
person touched the motor and shroud at the same time. After adding
grounding wires and checking the motor wiring buffer was still
shocking. Shocks stopped when I disconnected the light wiring(buffer
motor, lights and exhaust on this machine are all connected to one
switch). I checked the light sockets and found one mounting screw
loose and connecting with the bulb putting power to the shroud.
Touching shroud and motor at the same time completed the circuit. I
tightened the light mounting screws and shocks stopped.


#11

Someone mentioned grounding the frame… Just would like to relate a
short story. I had thrift store purchased an ancient electric
blender. It worked fine, looked cool, but gave a mild electric shock
especially when barefoot.

So, being the clever guy I am, I replaced the two prong cord with a
three prong grounded cord and wired the ground to the body of the
blender. Smiling proudly I plugged in the blender and flipped the
switch, only to hear a muffeled pop followed by that nasty burning
wire smell. Smile faded…

Good luck


#12

Mark,

Well look at the good side the grounded cord did it’s job, and
possibly saved your life in the process.

The problem was a short between the blender wiring and the case. When
you touched it, the electricity went from your hand trough your
chest to your feet (You were the third wire)… Now all it would have
taken was a bit of water on the floor so has to give your feet a good
enough contact and the amount (amperage) of the electricity passing
trough your heart would have been enough to stop it.

So in short be happy you are alive even if the blender is not.

Kay

PS next time do both… Fix the internal ground short and put a
grounded wire on, that way you will have safety and a blender


#13

Static shocks are pretty common with buffers and belt sanders. This
is how Van DeGraph static electricity generators that make peoples
hair stand on end work. You probably are wearing insulating shoes,
and/ or are standing on a mat to insulate yourself from ground. A
couple things that work for me is to touch the motor with the metal
part after polishing so that the spark occurs there, or to touch the
palm of my hand to the painted surface of the buffing motor. The
extra area of your hand over the painted surface seems to dissipate
the charge more slowly, so doesn’t cause the same spark that you
might get by touching the switch or other grounded item. It is very
humidity dependant, and also depends a lot on what’s being polished.
I get the nastiest sparks when sanding dry powdery wood on a belt
sander. When reaching for the off switch, they can jump around 3/8"
to bite me. They can be something like 50,000 volts, so it’s best to
dissipate the voltage before touching something grounded. As has been
mentioned, you can wear or lean against a static dissipating surface.

Bruce Boone
Boone Titanium Rings
http://www.boonerings.com/
770-645-6488


#14

Hi Judy,

As you can see I’m about a month behind in reading the list emails.

I have a similar problem with my buffing machine (a converted bench
grinder) that I purchased new 2-3 years ago.

From your description I think that you are simply building a static
charge up as you buff, much like my machine does. If there was a
problem with the housing being electrified it would likely also
occur when the machine was turned off, or when turned on but before
any buffing has happened. A multimeter capable of measuring AC
voltages could confirm or rule out these possibilities.

Being in the computer industry (my day job) I am familiar with
static electricity and its hazards to electronic components.

What I did is add a static strap to the buffing area. If you haven’t
seen one they are usually an elasticized bracelet with an internal
resistor and a snap clip, and a wire with an matching snap clip on
one end and an alligator clip on the other end. Clip the alligator
end to something that is electrically grounded; the motor housing
(make sure the power cord has the third prong and is connected to the
housing, again with the multimeter) or a cold water pipe. There are
other grounds available if you are certain the electrical circuit is
wired properly.

Put the static strap on your wrist before buffing

The resistor is very important, it is what slows down the discharge
of current. Do not try just a piece of wire as this can be hazardous
if the insulation inside the motor fails and the housing does become
electrified.

If you have any further questions please do not hesitate to ask,

Mike O’Toole