A wide variety of mechanical motions
and actions may present hazards to those
working around industrial machines. 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.
According to OSHA, the basic types of
hazardous mechanical motions are rotating,
in-running nip points, reciprocating and
transversing; actions are cutting, punching,
shearing and bending.
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.
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.
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.
Nip points can occur between rotating
and fixed parts that 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.
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.
Transverse motion (movement in
straight, continuous line) creates a hazard because a worker may be struck or caught
in a pinch or shear point by the moving part.
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 band saws,
circular saws, boring and drilling machines,
turning machines (lathes), or
milling machines.
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.
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.
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.
Safeguards must meet these minimum
general requirements:
