Accident Prevention Manual
for Business & Industry:
Engineering & Technology
13th edition
National Safety Council
Compiled by
Dr. S.D. Allen Iske, Associate Professor
University of Central Missouri
CHAPTER 23
METALWORKING MACHINERY
Metalworking Machinery
• Power-driven machines not movable by hand
• Metalworking machinery is used to shape or form metal
by cutting, impact, pressure, electrical techniques,
chemicals techniques, or a combination of these
processes.
• Association for Manufacturing Technology (AMT) has
classified 200 types of machines into five groups
• Turning
• Boring
• Milling
• Planing
• Grinding
• Other: electrodischarge, electrochemical, laser, machining tools
Metalworking Machinery (Cont.)
• Injuries
• caused by unsafe working practices or incorrect procedures
• insufficient training
• inadequate supervision
• injuries due to machine mechanical failures or operation after
unsafe conditions develop are rare
• Prevention of injuries
• only qualified competent personnel should operate
• properly maintaining and operating equipment
• effective guarding devices
• good housekeeping
• good work habits
General Safety Rules
• Emphasize safely operating metalworking machinery.
• Establish written policy.
• Restrict operation, adjustment, and repair of machine tool to
authorized, experienced, and trained personnel.
• Ensure proper power lockout/tagout.
• Closely supervise all personnel during training.
• Establish and maintain safe work procedures.
• Prohibit shortcuts and chance taking.
General Safety Rules (Cont.)
• When purchasing new equipment, make sure the
specifications are applicable to all standards, codes, and
regulations concerning guarding, electrical safety, and
other safeguards
• Inspect any modified equipment and make safety
innovations before allowing operators to use the
equipment.
• Devote full-time attention to the work in progress.
• Make supervisors responsible for the strict enforcement of
this policy.
• ANSI/NFPA 70 and ANSI C2 should govern installation of
electrical circuits and switches.
General Safety Rules (Cont.)
• Electrical controls on machine tools
• Disconnect switch can be locked in OFF position to isolate the
machine from power source.
• Do not permit maintenance or repair on any machine until the
disconnect switch serving the equipment has been shut off,
padlocked in the OFF position, and tagged.
General Safety Rules (Cont.)
• Rules for safely operating machine tools
• Never leave machine tools running unintended, unless the
machine has been designated to do so.
• Never wear jewelry or loose-fitting clothing.
• Keep long hair covered.
• Wear eye protection.
• Do not contaminate metal removal fluid.
• Do not manually adjust and gauge work while machine is
running.
• Use brushes, vacuum equipment or special tools for removing
chips. Do not use hands.
• Use the proper hand tool for each job.
• Know health and fire hazard of working with metals.
General Safety Rules (Cont.)
• Safely removing chips, shavings, and cuttings
• A major cause of accidents is use of high-pressure compressed air
to blow chips, cuttings, or shavings from machines or worker’s
clothing.
• In cases where neither a brush or a vacuum is practical, it may be
necessary to use air.
• Isolate the machine tool operation so that nearby employees are
not endangered.
• Place chip guards around the machine to shield the operator.
• Employees should wear PPE: safety goggles, face shield, body clothing
• Prohibit employees from using high-pressure compressed air to blow
dust or dirt from clothing and hair.
• One company has eliminated injuries caused by removing chips,
shavings, or cuttings.
• Employees wear leather palmed gloves and use a 3-ft-long rod to pull
shavings and cutting from the machines.
General Safety Rules (Cont.)
• Personal protection
• The operator’s safety depends on following safe working
procedures and wearing proper protective clothing and
equipment.
• Wearing close-fitting clothing is important.
• Many serious injuries and fatalities have resulted when neckties, loose
shirtsleeves, gloves or other clothing have gotten caught in a belt and sheave,
between gears, in a revolving shaft or revolving work piece held in the chuck.
• Operators should not wear jewelry that might get caught in machinery.
• Every operator should wear protective footwear.
• Operators with long hair should wear caps, snoods, or hairnets.
• Use splash guards, shields, PPE to minimize exposure to irritating
cutting oils and mineral spirits used to clean parts.
• Provide barrier creams and encourage personal hygiene measures.
Turning Machines
• Shaping a rotating piece with a cutting tool, usually to give
a circular cross section is known as turning. Engine lathes,
turret lathes, chuckers, automatic screw machines.
• Engine lathes
• Only qualified personnel to operate
• The following activities/situations are likely to result in injuries:
•
•
•
•
•
•
•
•
•
•
Having contact with projections on work or stock faceplates, chucks, or lathe dogs
Being hit by flying metal chips
Hand braking the machine
Calipering and gauging the job while machine is running
Failing to keep the center holes of taper work clean and true and the lathe’s center
true and sharp
Leaving the machine running unattended
Handling chips by hand
Attempting to remove the chips while the machine is running
Leaving the chuck wrench in the chuck
Catching rings, loose clothing, gloves, or rags for wiping or revolving parts
Turning Machines (Cont.)
• Engine lathe preventive measures
• Use faceplates and chucks without projections whenever possible.
• Install a shield formed to the contour of the chuck or plate and
hinged at the back.
• Substitute safety-type lathe dogs for projective setscrews.
• Chip shields help control flying chips.
• These shields do not eliminate the need for protective eye
equipment.
Turret Lathes and Screw Machines
• Hazards associated with turret lathes and screw
•
•
•
•
•
machines are similar to those listed for other lathes.
Additional hazards are caused by operators not moving
the turret back as far as possible when changing or
gauging work or using machine power to start the
faceplate or chuck onto the spindle.
Operators fail to keep their hands clear of the turret’s slide
or permitting a hand, arm, or elbow to strike the cutter
while adjusting or setting up.
Install splash shield, especially for automatic machines.
Enclosure shield over the chuck to confine hot metal chips
and oil splashes.
Install chip breakers to protect against hand and arm
injuries.
Spinning Lathes
• A spinning lathe is a forming tool rather that a cutting tool.
• Usually requires a skilled and qualified operator.
• Unsafe practices:
• Inserting blanks and removing the processed part without first
stopping the machine.
• Failing to fully tighten the tailstock handle and risking that the blank
will work loose or ruin the stock or tool.
• Allowing the swarf (cutting, turnings, particles) to build up into a
long coil when trimming copper and certain grades of steel.
• Accidents (severed hands and severely cut arms):
• Coil became snarled in an operators neck.
• Operators should remove the tool when necessary to allow the
swarf to break off.
• Spinning lathes reach speeds from 500 to 2,000 rpm.
•
Prevention of injuries lies in frequent inspection and maintenance of
chucks. Inspect for cracks in tools or handles.
Boring Machines
• Boring consists of cutting a round hole using a drill, boring
cutter, or reamer.
• Drilling machines are equipped with rotating spindles,
handles, and chucks that carry pointed or fluted cutting
tools.
• Operations performed with drilling machines include:
• countersinking
• reaming
• tapping
• facing
• spot facing
• routing
Drills
• Drill press accidents are more likely to occur during unusual jobs because
special jibs or vises for holding the work are not usually provided.
• Radial drill accidents are frequently caused by incorrect manipulation.
• Common hazards:
•
•
•
•
•
•
•
•
•
Contacting the rotating spindle or the tool
Being struck by a broken drill
Using dull drills
Being struck by insecurely clamped work
Catching hair, clothing, or gloves in revolving parts
Sweeping chips, or trying to remove long spiral chips by hand
Leaving the key or the drift in the chuck
Being struck by a flying metal chip
Failing to replace the guard over the speed-change pulley or gears
• When necessary guard the tool with a telescoping guard to cover the end of
the tool.
• A drill smaller that 1/8 in. in diameter will often break and cause injury.
• A frozen tool may cause unclamped or insecurely clamped work to spin and
injure the operator.
• If chips are allowed to pile up, the drill might jam, with results similar to that of
a frozen tool.
Boring Mills
• Common causes of injuries in boring mill operations:
• being struck by insecurely clamped work or by tools left on or near
the revolving table
• catching clothing or rags for wiping in revolving parts
• falling against revolving parts
• calipering or checking work while the machine is in motion
• allowing turnings to build up on the table
• removing turnings by hand
Horizontal Boring Mills
• Horizontal boring mills
• The same accident prevention activities are effective on both table
and floor types of horizontal boring mills.
• While the machine is in motion, the operator should never attempt to
make measures near the tool, reach across the table or adjust the
machine or the work.
• Frequently inspect clamps and blocking to make certain the clamping is
positive. Always avoid makeshift setups.
• Properly adjust by raising or lowering the boring mill’s head to avoid
damage to the machine or injury to the operator.
Vertical Boring Mills
• Vertical boring mills
• Each mill’s table, particularly those tables 100 in. or less in
diameter, should have the rim enclosed in a metal band guard to
protect the operator from being struck by the revolving table or
projecting work.
• If the table is flush with the floor, install a portable fence.
• While the machine is in operation, the operator should never
attempt to tighten the work, the tool, the caliper, nor measure the
work, feel the edges of the cutting tool, or oil the mill.
• The operator should never ride the table while it is in motion,
except if necessary by procedure to observe the work’s progress.
Milling Machines
• Machining a piece of metal by bringing it into contact with
a rotating multi-edged cutter is milling.
• This procedure is done by horizontal and vertical milling
machines, by gear hobbers, profiling machines, circular
and band saws and a number of other types of related
machines.
Milling Machines (Cont.)
• Causes of injuries:
• Failure to draw the job back to a safe distance when loading or
•
•
•
•
•
•
•
•
•
•
•
•
•
unloading
Using a jig or vise that prevents close adjustment of the guard
Placing the jig or vise-locking arrangement in such a position that force
must be exerted toward the cutter
Leaving the cutter exposed after the job has been withdrawn
Leaving hand tools on the workable
Failing to securely clamp the work
Reaching around the cutter or hob to remove chips while the machine
is in motion
Removing swarf cuttings by hand instead of with a brush
Calipering or measuring the work while the machine is working
Using a rag to clean excess oil while the cutter is turning
Incorrectly storing cutters
Cleaning the machine while in motion
Misjudging clearances between the arbor or other parts
Wearing improper clothing or jewelry around milling machine
Basic Milling Machines
• To guard the cutter, mount hand-adjusting wheels, for
quick or automatic transverse on some models, on the
shaft by either clutches or ratchet devices. In this way, the
wheels do not revolve when the automatic feed is used.
• The horizontal milling machine should have a splash
guard and pans for catching ejected metalworking fluids
or lubricants running from the tools.
• When possible, make all cuts into the travel of the table
rather than away from the direction of travel.
Metal Saws
• Circular saws
• They should have a hood guard at least as deep as the roots of the
•
•
•
•
teeth.
The guard should automatically adjust itself to the thickness of the
stock being cut.
Use a sliding stock guard when tube or bar stock is cut.
Guard the portion of the saw under the table with a complete
enclosure that provides for disposal of the scrap metal.
Do not consider a guard as a substitute for eye protection.
Metal Saws (Cont.)
• Swing saws
• Adjust the length of the stroke so the blade will not pass the table at
its most forward point.
• Locate the control so the saw can be operated with the left hand
when fed from the left or with the right hand if fed from the right.
• Operator positioned to the side away from the moving table.
• Band saws
• Completely enclose the upper and lower wheels of metal-cutting
band saws with sheet metal or a heavy, small-mesh screen
mounted on angle-iron frames.
• Provide access doors equipped with latches.
• The length of the blade exposed should not be more than the
thickness of the stock plus 3/16 in.
• On a hand-fed operation, take care at the end of a cut.
• Use a push block not hands.
Gear Cutters
• Gear cutters
• When operating cutters and hobbers, both the tool and workpiece
move.
• Keep the point of operation guards simple and easily adjustable.
• On operations where the workpiece is moved to the tool, a simple
barrier guard, formed to cover the point of operation and sized to fit the
workpiece is satisfactory.
• Locate all controls for protection of the operator and ease of function.
• Electrical discharge machinery (EDM)
• This process is designed to perform a variety of machining operations.
• This process makes simple or complex machining possible through
hole boring or cavity sinking in any electrically conductive work
material.
Electrical Discharge Machining
• Discharge gases hazard
• Operators and maintenance personnel should completely
understand all the precautions before operating, setting up,
running, or performing maintenance on EDM machines.
• Failure to comply with instructions may result in serious or fatal
injury.
• The operator should be aware of the possibility of discharge gases
igniting.
• Turn off the electrical power to stop additional gas or hot metal
particles from forming to extinguish a flame.
• All discharge gases are flammable keep them away from sparks or
flame.
Planing Machines
• Planers machine metal surfaces.
• The cutting tool is held stationary while the workpiece is
moved back and forth underneath it.
• With shapers classified as planing machines, the process
is reversed.
• The workpiece is held stationary while the cutting tool is moved
back and forth.
• Other machine tools classified as planing machines are
slotters and broaches.
Planers
• Accidents result from unsafe practices by inadequate
training and supervision such as the following:
• placing hands or fingers between the tool and the workpiece
• running the bare hand over sharp metal edges
• measuring the job while the machine is running
• failing to clamp the workpiece or tool securely before starting the cut
• riding the job
• having insufficient clearance for the workpiece
• coming in contact with reversing feed dogs
• failing to make sure the current is turned on before starting the
machine.
• unsafely adjusting the tool holder on the cross head
• To avoid these accidents, install guards in planers. Cover
the feed dogs on planers.
Shapers
• Accidents with shapers are essentially the same as
•
•
•
•
planers.
In addition, injuries from contact with projections on the
workpiece or with projecting bolts or brackets.
Shaper operators should make sure the tool is set.
Remove the handle of the stroke-change screw before
starting the shaper.
To prevent injury to the operator and workers nearby from
flying chips, install guards.
Planers and Shapers
• Slotters
• Most serious accident is catching the fingers between the tool and
the workpiece.
• Fingers can be caught between the ram and the table when the
ram is at the end of the downstroke.
• Broaches
• Rated capacity should be equal to or greater than the force
required for the job.
• Two-hand controls and install Emergency Stop.
Grinding Machines
• Grinding machines shape material by bringing it into
contact with a rotating abrasive wheel or disk.
• Grinding includes:
• surface, internal, external cylindrical, and centerless operations, as
well as polishing, buffing, honing, and wire brushing
• Reference ANSI Standards: B7.1 Use, Care and
Protection of Abrasive Wheels and B11.9 Safety
Requirements for the Construction, Care and Use of
Grinding Machines
Grinding Machines (Cont.)
• Hazards:
• Failure to use eye protection and eye shield mounted on grinder
• Incorrectly holding the work
• Incorrectly adjusting the work rest
• Using the wrong type of wheel or disk
• Grinding on the side of the wheel not designed for grinding
• Taking too heavy a cut
• Applying work too quickly to a cold wheel or disk
• Grinding too high above the wheel’s center
• Vibration and excessive speed that lead to bursting a wheel or disk
• Contacting unguarded moving parts
• Incorrect wheel dressing
• Contacting unguarded moving parts
• Using controls that are out of the operator’s normal reach
• Using an untested, broken, or cracked grinding wheel
• Using an abrasive blade instead of a grinder disk
Abrasive Disks and Wheels
• An abrasive disk is made of bonded abrasive, with
inserted nuts or washers, projecting studs, or tapped plate
holes on one side of the disk. The side is mounted on the
faceplate of a grinding machine.
• Only the exposed flat side is designed for grinding.
• Inspecting abrasive disks and wheels
• When unpacking abrasive disks, inspect for damage from
shipment, and have a qualified person give them the “ring” test.
• Conduct daily inspection of grinding machines. Thoroughly
investigate grinding wheel and disk failures.
Abrasive Disks and Wheels (Cont.)
• Handling abrasive disks and wheels
• These disks require careful handling.
• Do not drop or bump them.
• Do not roll large disks and wheels on the floor.
• Transport disks and wheels too large or heavy to be manually
carried by hand truck or other means that provide support.
• Storing abrasive disks and wheels
• Store them in a dry area not subject to extreme temperature
changes, especially below-freezing temperatures.
• Breakage can occur.
• Store them in racks in a central storage area under the control
of a specially trained person
• The storage area should be as close as possible to the grinding
operations to minimize handling and transportation.
• Follow manufacturer recommendations for storage length.
Abrasive Disks and Wheels (Cont.)
• Mounting Wheels
• Mount all abrasive wheels between flanges.
• Schedule flange inspections frequently.
• An incorrectly mounted abrasive wheel is the cause of much wheel
breakage.
• Before the wheel is mounted, give it the same inspection and ring
test as it was given when originally received and stored.
• Check the bushings, particularly on wheels that have been
rebushed by the user for shifting or looseness.
• Immediately after mounting the wheel and before turning on the
power, the operator should turn the wheel by hand for a few
revolutions. Check to make sure the wheel clears the hood guard
and machine elements.
Abrasive Disks and Wheels (Cont.)
• Operating a grinding machine
• When starting a grinding machine, stand on one side away from
the grinding wheel.
• Allow at least 1 minute of warm-up before truing and grinding with
the wheel.
• Always use coolant when truing the wheel or during normal
grinding.
• While the machine is running, never remove a guard fastener or
guard.
• Do not touch any moving part of the machine or the rotating
grinding wheel.
• Do not attempt to manually operate a machine that is automatic.
Abrasive Disks and Wheels (Cont.)
• Adjusting safety guards
• The guard should enclose the wheel as completely as the nature of
the work will permit.
• Adjust the peripheral guard to the constantly decreasing diameter
of the wheel with an adjustable tongue or similar device.
• On machines used for cutting, grooving, slotting or coping stone or
other materials, the safety guard or hood seldom offers adequate
protection.
• Safe speeds
• Do not operate at speeds exceeding those recommended by the
manufacturer .
• Unmarked wheels of unusual shape, such as deep cuts with thin
walls or backs with long drums, follow the manufacturers
recommendations.
Abrasive Disks and Wheels (Cont.)
• Work rests
• The work rest should be substantially constructed and securely
clamped not more than 1/8 in. from the wheel.
• Check work rest’s position frequently .
• Never adjust the work rest while the wheel is in motion.
• Dressing abrasive wheels
• Abrasive wheels that are not true or not in balance will produce
poor work.
• They can damage the machine and injure the operator.
• Keep wheels in good condition.
• Equip wheel-dressing tools with hood guards over the tops of the
cutters.
Surface Grinders and Internal Grinders
• Surface grinders and internal grinders
• Operating requirements for surface grinders and internal grinders
differ from those of other types of wheels.
• Insecurely clamped work pieces and un-energized magnetic
chucks are common sources of injury to operators.
• If the operator takes too deep a cut or too quickly traverses the
table or wheel too quickly, the wheel can overheat at the rim and
crack.
• Train operators and supervise operators to clamp work tightly.
• Must control the work’s speed and depth.
• Provide for some provision of exhausting the grinder dust.
Grindstones
• Grindstones
• When using grindstones, follow the manufacturer’s suggested running
speeds and operating procedures.
• Never run stones of unknown composition or manufacturer at more than
2,000 sfmp.
• The size and weight of grindstones requires a stand that is rigidly
constructed and heavy enough to hold the stone securely and mounted
on a solid foundation to withstand vibration.
• Since grindstones are run wet, take all possible precautions to prevent
slipping accidents.
• Carefully inspect grindstones for cracks and other defects.
• Many grindstone failures result from faulty handling and incorrect
mounting.
• Do not leave grindstones partially submerged in water.
• This causes the stone to unbalance and can break when used.
• Provide an adequate exhaust system.
Polishing Wheels and Buffing Wheels
• Polishing wheels and buffing wheels
• Polishing wheels are either wood faced with leather or made of
stitched-together disks of canvas or similar material.
• Buffing wheels are made of disks of felt, linen, or canvas. The
periphery is given a coat of rouge, tripoli or other mild abrasive.
• The softness of the wheel, build up of linen, canvas, felt or
leather, is determined by the size of the flanges used.
• Do not place the wheel on the spindle with a file or other object
held against it. This file could catch in the wheel and be thrown
with such force that nearby workers are injured.
Polishing Wheels and Buffing Wheels
• Mounting
• Mount these wheels in rigid and substantially constructed stands
that are heavy enough for the wheels used.
• Speed
• Speed range is from 3,000 to 7,000 sfpm with 4,000 sfpm in
general use for most purposes.
• Safeguards
• Hood guards should be designed to prevent operators hands or
clothing from catching on protruding nuts or ends of spindles.
• Exhaust hoods should be designed to capture particles thrown off
by the wheels.
• Never substitute a prick punch and hammer for a spanner wrench.
• Operators of polishing wheels and buffing wheels should not wear
gloves.
• Operators should not attempt to hold small pieces against the
wheel with bare hands.
Wire Brush Wheels
• Wire brush wheels
• Are scratch wheels used to remove burrs, scale, sand, and other
materials.
• These wheels are made of different protruding wires with different
thicknesses.
• Do not exceed the recommended speed.
• The hood on scratch wheels should enclose the wheel as
completely as the nature of the work allows.
• PPE is especially important because the wires tend to break off.
• Make it mandatory for the operators to wear aprons made
of leather, heavy canvas, leather gloves, face shields, and
goggles.