A wide variety of mechanical motions and actions may present hazards to the worker. These can include the movement of rotating members, reciprocating arms, moving belts, meshing gears, cutting teeth, and any parts that impact or shear. These different types of hazardous mechanical motions and actions are basic in varying combinations to nearly all machines, and recognizing them is the first step toward protecting workers from the danger they present. The basic types of hazardous mechanical motions and actions are:
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| Rotating |
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Rotating
motion can be dangerous; even smooth, slowly rotating shafts
can grip hair and clothing, and through minor contact force the hand
and arm into a dangerous position. Injuries due to contact
with
rotating parts can be severe.
Collars, couplings, cams, clutches, flywheels, shaft ends,
spindles, meshing gears, and horizontal or vertical shafting are
some examples of common rotating mechanisms which may be hazardous.
The danger increases when projections such as set screws, bolts,
nicks, abrasions, and projecting keys or set screws are exposed on
rotating parts.
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Examples of Hazardous Projections on Rotating Parts |
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Rotating coupling with
projecting bolt heads
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Rotating shaft and
pulleys with projecting key and set screw
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| In-Running
Nip Points |
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In-running nip
point hazards are caused by the rotating parts on
machinery. There are three main types of in-running nips.
Parts can rotate in opposite directions while their axes
are parallel to each other. These parts may be in contact
(producing a nip point) or in close proximity. In the
latter case, stock fed between two rolls produces a
nip point. As seen here, this danger is
common on machines with intermeshing gears, rolling mills,
and calenders.
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Common nip
points on rotating parts |
Nip points are also created between rotating and
tangentially moving parts. Some examples would be: the point
of contact between a power transmission belt and its pulley,
a chain and a sprocket, and a rack and pinion.
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Nip points
between rotating elements and parts with longitudinal
motions |
Nip points can occur between rotating and fixed parts
which create a shearing, crushing, or abrading action.
Examples are: spoked handwheels or flywheels, screw
conveyors, or the periphery of an abrasive wheel and an
incorrectly adjusted work rest and tongue.
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| Nip points between rotating machine components |
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| Reciprocating |
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Reciprocating motions may be hazardous because, during the back-and-forth
or up-and-down motion, a worker may be struck by or caught between a
moving and a stationary part. |
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Worker Caught Between a Reciprocating Table Piece and a Stationary Part |
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| Transversing |
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Transverse motion (movement in a straight,
continuous line) creates a hazard because a worker may be struck or
caught in a pinch or shear point by the moving part.
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Transverse motion of belt
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| Cutting |
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Cutting action may involve rotating,
reciprocating, or transverse motion. The danger of cutting action
exists at the point of operation where finger, arm and body injuries
can occur and where flying chips or scrap material can strike the
head, particularly in the area of the eyes or face. Such hazards are
present at the point of operation in cutting wood, metal, and other
materials. Examples of mechanisms involving cutting hazards
include bandsaws, circular saws, boring and drilling machines,
turning machines (lathes), or milling machines. |
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Hazardous drilling action
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| Punching |
Punching action results when power is
applied to a slide (ram) for the purpose of blanking, drawing, or
stamping metal or other materials. The danger of this type of action
occurs at the point of operation where stock is inserted, held, and
withdrawn by hand.
Typical machines used for punching operations are
power presses and iron workers.
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Typical punching operation
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| Shearing |
Shearing action involves applying power to a slide
or knife in order to trim or shear metal or other materials. A hazard occurs at the point of operation where stock is actually inserted, held, and withdrawn.
Examples of machines used for shearing operations are
mechanically, hydraulically, or pneumatically powered shears.
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Typical shearing
operation
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| Bending |
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Bending action results when power is
applied to a slide in order to draw or stamp metal or other
materials. A hazard occurs at the point of operation where stock is
inserted, held, and withdrawn.
Equipment that uses bending action includes power
presses, press brakes, and tubing benders.
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Typical bending
operation
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