Chapter Five - General
Shop Equipment and Machinery
CHESS has a variety of equipment in its machine
shop, each with potential hazards. Before using any equipment
in the shop, you must be trained to use it and checked out by the
Machine Shop Supervisor.
General Guidelines for Shop Safety:
Eye Protection: grinding, cutting
and drilling of metal and wood generate airborne particles.
Always wear safety glasses, goggles, or shields.
Foot Protection: always wear sturdy,
closed-toed shoes to protect your feet from wood and metal wastes on
shop floors, and from heavy objects that can crush feet and toes.
A safety shoe and boot truck visits CHESS regularly - check with
your supervisor or the Shop Supervisor for information on where to
buy safety shoes. CHESS personnel are allowed to purchase one
pair of safety shoes annually.
Hand Protection: to prevent cuts,
burns, sprains and repetitive motion injuries, be proactive about protecting
yourself. Wear appropriate gloves (unless you are using equipment with unforgiving
rotating parts), and remove watches and jewelry before you start work.
Don't handle shop chemicals or operate machinery with your bare hands, and don't
ignore safety guards on machinery. Always inspect equipment and machinery for wear,
dull cutting blades, or broken parts before you begin work.
Use the correct tool for the job. If you are lifting and
carrying heavy objects, be aware of narrow doorways where your hands
can get caught and crushed: when stacking heavy objects, keep your
hands on either side, not underneath, to avoid crushing your
Clothing: be aware, especially when
working with equipment with moving parts, of hair and clothing that
could become trapped in machinery. Tie back long hair, remove
neckties, and roll up long sleeves. Wear a safety apron to
protect your body from flying particles of metal or wood.
Housekeeping: clean up after
yourself. Put away materials when you are finished with them.
Roll up power cords and return them to their appropriate storage
places. Do not leave machines running unattended.
Think ahead before you begin any
project: What are the steps necessary to complete it and what
are the potential hazards? Consider other people working in
your area and let them know if you are doing work that may create a
potential safety hazard for them.
Basics of Machine Safeguarding
Crushed hands and arms, severed
fingers, blindness - the list of possible machinery related injuries
is a long as it is horrifying. There seems to be as many
hazards created by moving machine parts as there are types of
machines. Safeguards are essential for protecting workers form
needless and preventable injuries.
A good rule to remember is:
Any machine part, function, or process which may cause injury must
be safeguarded. Where the operation of a machine or accidental
contact with it can injure the operator or others in the vicinity,
the hazard must be either controlled or eliminated.
This section describes the various
hazards of mechanical motion and action and presents some techniques
for protecting workers from these hazards.
Where Mechanical Hazard Occur
Dangerous moving parts in these
three basic areas need safeguarding:
The point of operation:
that point where work is performed on the material, such as
cutting, shaping, boring, or forming of stock.
Power transmission apparatus:
all components of the mechanical system which transmit energy to the
part of the machine performing work. These components include
flywheels, pulleys, belts, connecting rods, couplings, cams,
spindles, chains, cranks, and gears.
Other moving parts:
all parts of the machine which move while the machine is working.
These can include reciprocating, rotating, and transverse moving
parts, as well as feed mechanisms and auxiliary parts of the
Hazardous Mechanical Motions
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 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:
Brief examination of each of these
can be dangerous; even smooth, slowly rotating shafts can grip
clothing, and through mere skin contact force an arm or hand into a
dangerous position. Injuries due to contact with rotating
parts can be severe.
Collars, couplings, cams,
clutches, flywheels, shaft ends, spindles, and horizontal or
vertical shafting are some examples of common rotating mechanisms
which may be hazardous. The danger increases when bolts,
nicks, abrasions, and projecting keys or set screws are exposed on
In-running nip point hazards are
caused by 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 to each other. In the latter case the stock
fed between the rolls produces the nip points. This danger is
common on machinery with intermeshing gears, rolling mills, and
Another nip point is 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, or a rack and pinion.
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.
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
(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
involves rotating, reciprocating, or transverse motion. The
danger of cutting action exists at the point of operation where
finger, head, and arm injuries can occur and where flying chips or
scrap material can strike the eyes or face. Such hazards are
present at the point of operation in cutting wood, metal, or other
materials. Typical examples of mechanisms involving cutting
hazards include bandsaws, circular saws, boring or drilling
machines, turning machines (lathes), or milling machines.
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 operant where stock is
inserted, held, and withdrawn by hand.
Typical machinery used for punching operations are power presses and
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. Typical
examples of machinery used for shearing operations are mechanically,
hydraulically, or pneumatically powered shears.
results when power is applied to a slide in order to draw or stamp
metal or other materials, and 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.
Requirements for Safeguards
What must a safeguard do to
protect workers against mechanical hazards? Safeguards must
meet these minimum general requirements:
The safeguard must prevent hands, arms, or any other part of a
worker's body from making contact with dangerous moving parts.
A good safeguarding system eliminates the possibility of the
operator or another worker placing their hands near hazardous moving
Workers should not be able to easily remove or tamper with the
safeguard, because a safeguard that can easily be made ineffective
is no safeguard at all. Guards and safety devices should be
made of durable material that will withstand the conditions of
normal use. They must be secured to the machine.
Protect from falling
objects: The safeguard should ensure that no objects
can fall into moving parts. A small tool which is dropped into
a cycling machine could easily become a projectile that could strike
and injure someone.
Create no new hazards:
A safeguard defeats its own purpose if it creates a hazard of its
own such as a shear point, a jagged edge, or an unfinished surface
which can cause a laceration. The edges of guards, for
instance, should be rolled or bolted in such a way that they
eliminate sharp edges.
Allow safe lubrication:
If possible, one should be able to lubricate the machine without
removing the safeguards. Locating oil reservoirs outside the
guard, with a line leading to the lubrication point, will reduce the
need for the operator or maintenance worker to enter the hazardous
All power sources for machinery
are potential sources of danger. When using electrically
powered or controlled machines, for instance, the equipment as well
as the electrical system itself must be properly grounded.
Replacing frayed, exposed, or old wiring will also help to protect
the operator and others from electrical shocks or electrocution.
High pressure systems, too, need careful inspection and maintenance
to prevent possible failure from pulsation, vibration, or leaks.
Such a failure could cause explosions or flying objects.
Machines often produce noise (unwanted sound)
and this can result in a number of hazards to workers. Not only can
it startle and disrupt concentration, but it can interfere with communications,
thus hindering the worker's safe job performance. Research has linked
noise to a whole range of harmful health effects, from hearing loss
and aural pain to nausea, fatigue, reduced muscle control, and
emotional disturbances. Engineering controls such as the use of sound-
dampening materials, as well as less sophisticated hearing protection,
such as ear plugs and muffs, have been suggested as ways of controlling
the harmful effects of noise. Vibration, a related hazard which can
cause noise and thus result in fatigue and illness for the worker, may
be avoided if machines are properly aligned, supported, and, if necessary,
Because some machines
require the use of cutting fluids, coolants, and other potentially
harmful substances, operators, maintenance workers, and others in
the vicinity may need protection. These substances can cause
ailments ranging from dermatitis to serious illnesses and disease.
Specially constructed safeguards, ventilation and protective
equipment and clothing are possible temporary solutions to the
problem of machinery-related chemical hazards until these hazards
can be better controlled or eliminated form the workplace.
Even the most
elaborate safeguarding system cannot offer effective protection
unless the worker knows how to use it and why. Specific and
detailed training is therefore a crucial part of any effort to
provide safeguarding against machine-related hazards. Thorough
operator training should involve instruction or hands-on training in
a description and
identification of the hazards associated with particular machines;
themselves, how they provide protection, and the hazards for which
they are intended;
how to use the
safeguards and why;
how and under what
circumstances safeguards can be removed, and by whom (in most cases,
repair or maintenance personnel only; and
what to do (e.g.,
contact supervisor) if a safeguard is damaged, missing, or unable to
provide adequate protection.
This kind of safety
training is necessary for new operators and maintenance or setup
personnel, when any new or altered safeguards are put in service, or
when workers are assigned to a new machine or operation.