pdp1@EARTHLINK.NET on sat 3 mar 07
Hi all...
There are three things to my mind having to do with respecting the use of
Electric Bench Grinders -
1) The Wheels can sometimes disintegrate when the Motor is starting up and
coming up to speed. This, usually, if someone or something has bumped into
and cracked the Wheel from the side, since the last time it was run.
If this happens, fragments of the disintegrating Abrasive or Vitreous Wheel
can fling
out undramatically and sort of just plop out dully, or, some of them can
stay in the bottom or rear of the Guard, or, the semi-fractured or cracked
Wheel can wait a little, staying together as it comes up to speed, resisting
the centifical forces even at full RPM for a few moments anyway, to then
fail, disintegrate, and fling out large pieces of itself at quite high or
even full speed RPM.
If at quite high speed, or full speed of RPM, the presence of a Safety-Guard
which on many models of Bench Grinders covers much of the top and rear
periphery, depending on how the Guard is set to occupy what segment of the
periphery, the pieces will tend to fly out fairly horizontal or lowish, and
of course anything in their path can be harmed or injured by them.
If running no Safety-Guard, then the pieces can fly out in any direction,
and this can kill you or cause perhaps some terrible or at least unpleasant
injury if they hit you
in the face or head.
"Ogrish" dot com when it was it's own un-adorned wacky macabre web-site,
used to have
many interesting and instructive close-up and other images of various
industrial and machinery
related fatalities and non-fatal if gruesome mis-haps, and Abrasive Vitreous
Wheel
fragmentation events sometimes among them. One could see quite plainly what
a suitably large fragment of regular six or eight inch by one inch Grinding
Wheel can do if it disintegrates at speed and the pieces fly out at the
unfortunate angle to hit you in the Eye or Nose or Forehead or Mouth or in
the Balls or Stomach or Hip or Solar Plexis or anywhere really.
Hence, the prudent practice, whenever starting up a Bench Grinder having
Abrasive Vitreous Wheels on it, is to always stand a little to one side,
and, to make
sure you are satisfied that the 'path' the possible fragments could take, is
widely clear of people, Animals, yourself, or items that could be harmed IF
the Wheel were to disintegrate.
As far as I know, incidents of a Wheel disintegrating well AFTER it has
assumed full RPM, have only resulted from some extreme side-stresses of some
kind, usually, of
someone pressing some item to be Ground against the 'side' of a conventional
Abrasive Wheel, and pressing way too hard ( on what might be a glazed from
use, and un-dressed surface ) which are not really intended to be Grinding
from their sides anyway, or, which will Grind from their sides just fine,
but one
should never press things against them with too much force if doing so.
Possibly, any bits of crud or something interfering with the fit of the
Containment 'flanges' against the Wheel, when mounting a Wheel to the Shaft,
if the Nut is tightened up hard and there is something between the Flange(s)
and the Wheel, this might just be able to make stresses which could result
in an eventual subtle cracking and sub-sequent fragmentation of the Wheel at
speed. Hence, whenever mounting
a Wheel, or prepairing to use a Bench Grinder which someone else has had
sitting there but that YOU did not mount the Wheels on, consider to inspect
and make sure the central parts of the Wheel sides are clean and smooth,
insoect the Wheel itself, see if it has a 'dull' sound it lightly tapped,
which may mean it is cracked somewhat, and make sure the inside surfaces of
the Flanges are both of them clean and smooth and true...and that the Nut is
tightened "just' nicely enough to hold things well and surely, and is not
'too' tight.
Conventional Grinding or Abrasive Vitreous Wheels are made to accept
stresses from
things being pressed to whatever degree against their rim or edge, radially,
or in line with the tangent of their Rotation...and in this manner of use, I
doubt any such Wheel has ever failed no matter how aggressivly one jams
things into it. If one hit "this" edge sharply with a Hammer or something at
full RPM, maybe one could cause the Wheel to break apart from the shock and
stress of doing that, but not from 'pressing' items into or against it.
Those Wheels which have disintegrated at speed from causes not related to
present or discrete ( crud on both flanges diferentially arranged to be
causing the center of the Wheel to be asked to 'bend' under a tight Nut)
side-stresses, as far as I know, have done so within a few
seconds of start-up...where, I am certain, someone or something had bumped
them from the side while they were "off" and stresed them to some amount of
fine fracture or partial fracture, to where the welling stresses then in
comeing up to speed, or reaching speed, very soon caused the small partial
fractures to become large or full enough for the Wheel to fail to stay
together, and for these pieces to fly apart from the centrifical forces of
1,750, or, more usualy, of 3,500 RPM.
So, I would say, "always" start a Bench Grinder having such Wheels by
standing to one side...and, let it come up to speed for a minute or so, and
"then" commence your operations with it, and not sooner.
And, do not stress any such 'regular' Vitreous Wheels by grinding things
against their sides
unless one does so with only light pressing of the item into or against it.
Too, the 'thinner' the Abrasive Wheel is in width, the less one ought to
stress it from
the side in one's grinding operations.
And, for that matter, try and stand just somewhat to the side anyway while
Grinding, especially to have your face and head somewhat to one side, in
general, for any or all operations with these Machines.
Most people one can observe, stand right IN line with the Wheel, 'centered'
with it, THEN start it up, and they start Grinding immediately or even
before it has come up to full Speed...and with never a thought about others
standing in what would be the path of fragments should the Wheel fail...
This, as we can see, is very foolish...
2) Hair, String or similar thin soft flexible things if let to waft next to
the end of the Shaft or Axle the Grinding Wheel mount on...
Hair or String can get it's ends instantly winding around the Axel or Shaft
end, or with Wire Wheels, by just touching the Wires, and instantly reel
'in' whatever they are attatched to on their other end.
Again, "Ogrish" ( a worthless site now pretty much...but was pretty good at
one time, ) used to have images showing the results of this sort of thing
also,
and with Hair, usually Long or medium Hair is plenty strong enough to
effectively
reel in the person's head at whatever angle it happens to be, and almost
instantly too, with a more or less instant tearing off of their Scalp or
Scalp and some of their face or an Ear or something as well...as well as
possible serious concussion or abrasive erosions of having one's head or
face "in" the Wire Wheel or Grinding Wheel for a split before whatever is
going to get torn off, gets torn off. Let alone the unpleasant problems of
getting the torn off parts untangled from the Wire Wheel or Grinding Wheel's
shaft so they can be tidy'd up and stitched back on at liesure.
Hence, anyone with Long Hair which is free flowing, should not be allowed
anywhere near Bench Grinders when these machines are being operated.
People or operatives having medium length Hair or any but the shortest
Beards should remember to be very
circumspect if bending over to pick something up next TO such machines when
they are running...where their Head and Hair could end up close enough to
the Wire Wheel or Grinding Wheel to get into some trouble.
Air currents typically whirl around such Wheels and will gently pull 'in'
anything wafting close enough.
Operatives who have long or even medium length Hair should have their Hair
safely tucked into some Cap or otherwise made to be kept snug and put, so no
Hair in
any way can waft near the Axle or Shaft end under any possible exigency,
should they bend closer or
decide to pick up a dropped little item or in any way bend near the Wheels.
With these 'Hair' matters in mind, Dogs, Children, Women Hippies or anyone
happenning to pause to talk with someone
operating a Bench Grinder should immediately be told to stay well clear of
it and NOT to come close to be heard better or to converse or comment or be
hugged or petted or
anything whatever. If someone approaches to ask or talk, the operative
should instantly stand away from the Machine and direct the other to stay
back also...and yell one's conversational moment if need be, or, turn the
Machine "off'
and move away from it and THEN have your conversation or other interaction.
Large Dogs with long bushy Tails should not be let anywhere near when
running such Machines, especially if the Bench Grinder has Wire Wheels on
it.
Children of course who have long or medium length Hair already have their
Heads at the worst proximity for possible mis-haps...and of course should be
kept well clear of any such Machines being run.
Children should be nicely and earnestly convinced to enjoy the
self-regulated and cogent
responsibilty to never play with or turn on any Machines of any kind for
play
or curiosity or novelty, however it is one does so for them to be allright
with it and easy. They should not be led to fear these things, nor punished
or talked down to or yelled at or insulted for misdemeaners, but they should
be guided or
given the responsibility for merely leaving Machines alone out of some order
of regard for themselves and for the Machines, and encouraged to respect
themselves for their discipline TO do
so.
3) No one should be allowed to operate the Machines or portable Power Tools
of any kind which one
has say-so over, unless one is satisfied with the condition of these devices
and their salient parts, and one is satisfied with one's own and with the
other person's understandings of the
prudent use of them, and one is satisfied with the careful
presence-of-mind and intentional habits the use of such Machines should
inspire...no matter what prior
'experience' the person(s) may wish to have credit for.
Many people have
years of complaisent or shallow "experience" doing very foolish things...and
or doing them badly and or carelessly/thoughtlessly, with dangers to
themselves, to others and to the Machines...even IF they appear to have got
away with it so far.
That is my understanding and regimen...
Love,
Phil
el v
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