pdp1@EARTHLINK.NET on wed 11 jun 03
Some reminder about Electric Grinding Wheels, or, those as
turn at a fast R.P.M. anyway.
Long Hair may readily become wrapped around any rotating
arbor or axis...and...the faster the RPM of that axis, the
faster it may become wound, so one is well advised for
particular precautions to be observed
in this regard.
In settings where more than one person may operate the Bench
Grinder, or may do chores near to it, it is especially
useful to do a visual check of the Grinding Wheel itself
before starting the Grinder, to see if there are any signs
of damage, 'cracks' or appearant contusions or chips or
where something may have bumped into the Wheel.
If such signs are present, remove the Wheel and inspect it
more carefully off
the Machine.
If damaged with any cracks, discard it, or break it up and
use the pieces for something in the way of hand-work.
If a Wheel is going to 'explode', it will do so oweing to
it's having been cracked from some side force, as from
something having bumped it. Some very 'thin' wheels may be
compelled to break up in use, from extreme side pressures of
something being pushed against their side in
a much too forceful way while grinding.
A Six inch Wheel on a 3,500 RPM Bench Grinder, will have a
rim velocity of about 62 Miles per Hour, and an Eight inch
Wheel about 82 Miles per Hour...so, of one bears that in
mind, it is about like if 'Joplin Joe' DiMaggio were to have
thrown those pieces as may come your way, or, threw them on
an off day, seeing he could have got them passed the
'Century' mark I think...but regardless, it is fast enough
to kill you, or to change your personality, anyway.
If one is wishing to Grind on the side of a thin wheel, one
does well to do so with a pressure that respects the
Wheel's ability to resist it.
Generally, most Wheels are intended ONLY to resist forces
from their periphery as push 'in', and are not
intended for
resisting side-forces. Those Wheels whose design anticipates
side-forces will tend to be shaped like shallow 'cups', or
they may have a steel backing to them or be in some way
different for their purpose being different. Generally, the
wider a Wheel, the more side-forces it may be expected to
resist. (By 'wider', I mean thickness, and not diameter...)
If a vitreous Wheel is going to 'explode' or come apart at
all, it will tend to do so when the
Machine is first turned on, and the Wheel (and the Arbor to
which it is attached being an extension of the Motor's
armature) is accelerating to reach the running R.P.M. rate
of the
Motor.
Hence, when starting a Bench Grinder, one may wish to see
that there is nothing in line with the Wheel's rotation as
would be harmed in this eventuality. Allow the Grinder to
come up to speed and remain so a little before allowing
one's self or anyone else to be in line with the Wheel's
rotation. AND generally, as a pint of manners, do not allow
others to be in line with the Wheel's rotation at any time.
If, as the operative of the Grinder, you find it convenient
to be, do not oblige others to do so too, and, remind them
nicely if need be, should they situate themselves in line
with it.
No one I know of, nor I myself, have ever heard of any
Grinding
Wheel comeing apart at speed, except in instances of an
operative causeing extreme side pressures on that Wheel,
or the Wheel being hit hard from the side with something
while rotating.
I have seen Wheels disintegrate when comeing up to speed,
when the Grinder is first turned on, and I appreciate they
may do so
with startleing possibilities.
A simple regimen...is to just look at the condition of the
Wheel before turning on the Machine...and to then allways,
see to it that no one is in line with the rotation when it
is starting up...or no one 'else', once it is running, since
when one is grinding, one rather does tend to
stand in-line with the rotation.
Also...
Circular 'Wire Brushes' as may be mounted to Bench Grinders
may occasion opportunities of their own for potential
mis-haps, especially as concern 'Hair', which they will grab
with their wire-bristles
and wind up almost instantly, (or figure roughly, at the
rate of 91 to 122 feet per second. Which rate, one may
compare to the length of someone's 'long' hair to see how
long it would take before the length is run out )
and...also...one's scalp, or some of it anyway, tends
to get pulled off and wound up as well.
And while the attentions of a reconstructive-surgeon or
other
interested person with Sewing Skills may be
appealed to, for it to be sewn back on, it is a tedious
matter, and as well, an unpleasantness for bye-standers of
the mis-hap, or, for all concerned, or, were one alone, a
logistically trying matter
to get unwound by one's self.
Wire Wheels may also have a way of 'grabbing' certain shapes
or angles, or small 'parts', especially of things introduced
to them from above the wheel's mid-line.
The Wires should be understood to prefer to scrape 'away'
from sharp edges also, rather than on-to or in-to them.
Wire Wheels also shed broken or whole wires, and these may
stick in one's skin a little, or in one's clothing.
And, as the wires do not necessarily fly off in the
exact line of the Wheel's axis, one may have them strike
one's face even if standing somewhat to the side.
As I do not wear Safety-Glasses in these operations, I have
sometimes had a shed wire hit me in the eye, and while not
pleasant, it did not harm me either. Some Bench Grinders
have a 'Wheel Guard' as may be adjusted so as prevent these
sheddings from finding flight 'up' ward...
Now I tend to use Wire Wheels as have thin gauge wires, and
a heavy-gauge wire might just give me some troubles if it
flew into my eye, and if I were useing such a Wheel, I might
just put some 'glasses' on for this respect.
While the velocity of a light gauge wire being shed from a
3500 RPM Bench Grinder with a Six inch Wire Wheel, is enough
to just barely stick into one's skin at a few inches
distance from
the Wheel, it does not seem to have any precedent to do so
at the distance one's face tends to be.
By the time the shed (light gauge) wires have travalled a
few feet, they no longer seem to posess a velocity to be
more than noticed, should they strike one, or that is, no
more, say, than if dropped on one, or thrown by a Child.
If we understand 'what' we are doing, we may elect those
practices as best respect the eventualities and practice of
the task. I do not like things on my face ( 'Glasses',
'shields' etc...) or on my hands ('Gloves') when I am
Working, and If I may get along fine without them, I prefer
to do so.
This is not contempt, nor care-less-ness, nor spite, nor
ignorance, nor totemic inheritance or introjection from or
of how some elder or other progenitor had 'did-it'...
These are, or can be, choices made intentionally,
informedly, respectfully, as to how one understands their
Work, how one wishes to Work, and how one may wish to do so
as appreciatively as possible.
If you prefer to ensure safe practices, you must observe
them and understand 'why' and 'how' they are 'safe'.
Doing only part of something by rote, may not have the
advantage of understandings as would be the best assurance
of all.
Phil
lasvegas
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