Machine Guarding 271

Machine Guarding provides an OSHA-based comprehensive overview of general machine safeguarding practices associated with hazardous machine components, motions, and actions. In general, machine guards and safeguarding devices are considered primary safeguards against amputation and other injuries. Yet, feeding, ejection, and location are types of secondary safeguarding methods used in combination with guards and safeguarding devices.

Machine guarding is particularly important during times of inspection and maintenance. Hidden hazards from potential energy put an operator at risk even when a machine is turned off. To safeguard against this and human error, lockout/tagout procedures provide a strict set of safety guidelines for everyone to follow when performing maintenance tasks. After taking this course, users will be able to identify various machine motion hazards in the workplace and develop effective safeguarding strategies to prevent injuries.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 19

  • Language English


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Course Outline
  • The Importance of Machine Guarding
  • Mechanical Component Hazards
  • Machine Motion Hazards
  • Machine Action Hazards
  • Other Hazards
  • Machine Hazards Review
  • Basic Safeguard Standards
  • Primary and Secondary Machine Safeguarding
  • Types of Machine Guards
  • Safeguarding Devices
  • Primary Safeguarding Methods Review
  • Safeguarding by Feeding and Ejection Methods
  • Safeguarding by Distance and Location
  • Miscellaneous Machine Safeguarding Aids
  • Complementary Safety Equipment
  • Secondary Safeguarding Methods Review
  • Maintenance Safeguarding
  • Machine Safeguard Training
  • Final Review
  • Define machine guarding.
  • Describe mechanical component hazards.
  • Describe machine motion hazards.
  • Describe machine action hazards.
  • Describe other hazardous activity.
  • Describe basic safeguarding standards.
  • Distinguish between primary and secondary safeguarding methods.
  • Distinguish between different types of machine guards.
  • Describe safeguarding devices.
  • Describe machine safeguarding by feeding and ejection methods.
  • Describe safeguarding by distance and location.
  • Describe miscellaneous machine safeguarding aids.
  • Describe complementary safety equipment.
  • Describe maintenance safeguarding.
  • Describe machine safeguard training.
Vocabulary Term

adjustable guard

A barrier that may be moved or reconfigured to allow for different types of production. Adjustable guards can accommodate different sizes of stock or raw materials.


Loss of a limb or body part. Amputation is one of the most common and debilitating injuries caused by moving machine parts.

automatic ejection

A method for removing stock or parts from the point of operation on a machine. Automatic ejection occurs without operator contact.

automatic feed

A method of advancing a workpiece into a machine without operator contact. Automatic feed, also called autofeed, eliminates the need for operators to position their fingers or hands near the point of operation.

awareness barrier

A visual means of warning employees that they are entering hazardous areas. Awareness barriers include caution tape and yellow lines on a workplace floor.

bending action

The result of a downward or sideways punch-like movement using a blunt tool. Bending action is used to shape metal or other materials without cutting.

body bar

A touch-sensitive device that deactivates a machine when the operator applies pressure. Body bars are located on the machine periphery in order to stop the machine before a body enters the hazard area.


A circular or cylindrical component designed to make contact with another component while rotating. Cams may convert rotational movement into linear movement.


A small piece of material that is removed from a workpiece. Chips are formed when a tool cuts or grinds a material.

conveyor belts

A moving strip of material that carries parts or other components from one area of a manufacturing facility to another. Conveyor belts are commonly used to transport parts from production to packaging.

conveyor systems

A mechanical system consisting of a flexible belt and at least two fixed pulleys that is used to transmit motion. Conveyor systems should have their belts removed prior to maintenance work.

cutting action

The result of movement, such as rotation, of a tool with sharp cutting edges. Cutting action is used to remove material and make a cut.

emergency stop

E-stop. A pushbutton or switch that brings a machine to a safe and rapid stop. Emergency stops are important safety features that are intended to be used in case of emergencies.

face shield

A rigid, transparent plastic sheet that covers the worker's entire face to protect against dust or splashes. Because face shields do not protect against impacts, they are often worn with goggles.


The rate at which the cutting tool and/or the workpiece moves in relation to one another in a traditional manufacturing operation. Feeding is hazardous and should be safeguarded.

fixed guard

A barrier guard prohibiting access to dangerous operating areas while allowing operators to access parts of the machine. Fixed guards cannot be adjusted.


The device on a machine that spins continuously as the machine is powered up. flywheels store the energy necessary to cycle the machine when the clutch is engaged.

foot control

A machine start device that is activated with the operator's foot. Foot controls require guarding to prevent accidental activation.


A moveable physical barrier often used to safeguard metal cutting machines. Gates often have slides or hinges that allow them to be opened while remaining attached to the machine.

hazard analysis

A written, formal appraisal or assessment of the safety risks that exist within a workplace. A hazard analysis is often used to determine appropriate types of machine safeguarding.


A form of circular machine motion involving two or more mating parts. In-running can cause pinch-type injuries at the point where the parts converge.

interlocking guard

A set of doors that overlap or fit together to form a tight lock. Interlocking guards cover the point of operation to protect the operator from flying debris and fluid splashes.

light curtain

A field of light that stops a machine when the light is blocked by an object. Light curtains prevent mechanical parts from striking workers and equipment.


A method of protecting employees by preventing accidental machine startup through proper locking and labeling of machines during maintenance. Lockout/tagout is the common term for OSHA's Control of Hazardous Energy Standard.

machine guard

A rigid shield or cover that encloses hazardous areas on a machine. Machine guards prevent accidental machine contact with body parts and prevent debris, such as chips, from exiting the machine.

machine guard

A rigid shield or cover that encloses hazardous areas on a machine. Machine guards prevent accidental machine contact with body parts and prevent debris, such as chips, from exiting the machine.

machine guarding

The full variety of methods used to help prevent worker injury from machine hazards. Machine guarding methods keep body parts from entering hazardous areas of a machine and/or keep flying debris from exiting the machine.

machine safeguarding

The combination of safety methods and requirements in the manufacturing workplace. Machine safeguarding includes machine guards, safeguarding devices, and other tools and practices used to keep employees safe from machine hazards.

machine table

The surface on which stock or work is held and located on many types of machines. Machine tables are often capable of different types of movement.

mechanical failure

A condition in which a device loses its capacity to carry a load. Mechanical failure can be the result of gradual wear, insufficient lubrication, or overload.

metalworking fluid

MWF. The collective grouping of the most common coolant fluids used in metal cutting. Metalworking fluids include cutting oils, soluble oils, and chemical fluids.


A machine that uses a rotating multi-point tool to remove metal from the surface of a workpiece. Mills may be operated either manually or by computer numerical control (CNC).

nip point

The point where two rotating parts meet. Nip points can pinch or crush fingers or other body parts.


Any unwanted sound. Noise can occur over a short or long period of time.

Occupational Safety and Health Administration

OSHA. A government agency dedicated to reducing injuries, illnesses, and deaths in the workplace. The Occupational Safety and Health Administration sets standards to maintain accident-free workplaces.


Occupational Safety and Health Administration. A government agency dedicated to reducing injuries, illnesses, and deaths in the workplace. OSHA sets standards to maintain accident-free workplaces.

other moving parts

An OSHA category of moving machine components that pose hazards. Other moving parts include machine components, such as worktables or mechanical arms, that move in order to situate parts or tools.

personal protective equipment

PPE. Any clothing or device used to minimize exposure to hazards and prevent injuries. Personal protective equipment may include safety glasses, hard hats, and steel-toed shoes.

pinch point

Any place in which two moving components come together. Pinch points can cause injury if a body part comes into contact with the area.

point of operation

The area where the tool comes into contact with the workpiece. Point of operation is typically the most hazardous area of the machine and should be protected by primary safeguarding methods.

potential energy

Stored energy resulting from an object's position or internal pressure. Potential energy often exists in machines that have been turned off.

power transmission apparatuses

A device that facilitates the transfer of energy from a power source to an output device that performs work. Common power transmission apparatuses include gear trains, belt drives, and chain drives.

presence-sensing mat

A safety device that contains sensors to detect weight or pressure. Presence-sensing mats disengage the machine when activated by a predetermined amount of weight.


A machine tool that moves up and down to bend, shear, and shape sheet metal. Presses have a stationary base and an upper ram that moves along an axis to the point of operation where metalworking occurs.


A machine with a stationary base and an upper ram that moves along a vertical axis. Presses are often used to shear, bend, or form sheet metal.

press brake

A type of stamping machine with an open frame and wide, narrow bed. Press brakes are often used for bending operations, and they are typically manually operated.

primary safeguarding

A device or shield on a machine that prevents point of contact hazards. Primary safeguarding includes machine guards and safeguarding devices.


The process of entering digital information into a computer or computerized system. Programming involves the use of a machine interface and a programming language that can tell the machine what actions to perform.

pullback device

A wrist safeguarding device that prevents the hands of a machine operator from entering hazardous areas. Pullback devices pull back to pull the machine operator's hands away from the point of operation.


A type of simple machine consisting of a circular device that raises or lowers a load or transmits motion. Pulleys may be moveable or fixed.

punching action

A sheet metal shearing operation that creates a hole in metal stock. Punching action is also called piercing.

push stick

A hand-operated device, often made of wood. Push sticks allow the operator to feed stock into the point of operation while keeping hands out of harm's way.


The main upper portion of a press brake that slides up and down within the press frame during operation. The ram receives energy from a prime mover through power transmission components.

reciprocating motion

A form of back-and-forth or up-and-down machine motion. Reciprocating motion can cause crushing or pinch-type injuries.

restraint device

A wrist safeguarding device that restrains the hands of an operator during machine operation. Restraint devices prevent hands from crossing into the point of operation or other hazardous areas.


A programmable, multifunctional device that uses highly adaptable programmed motions to perform various processes. Industrial robots are a form of automation.

robotic arm

A programmable or remote-controlled mechanical device that simulates the movement of a human arm. Robotic arms are used in a variety of assembly and manufacturing applications.


A form of circular machine motion. Rotating motion such as with a spindle or wheel, can catch body parts, clothing, or hair.

safeguarding device

A switch, bar, sensor, or other mechanism that interrupts a machine's operating cycle. Safeguarding devices prevent workers or any parts of their bodies from entering dangerous areas during machine operation.

secondary safeguarding

Any device, barrier, or process that works with primary methods. Secondary safeguarding types include feeding and ejection, distance and location, and miscellaneous safeguarding aids.

self-adjusting guard

A barrier that covers a hazardous area until stock enters the point of operation. Self-adjusting guards move as the stock or cutting tool moves.

semi-automatic ejection

A method for removing stock or parts from the point of operation on a machine with limited operator intervention. Semi-automatic ejection is initiated by the machine operator.

semi-automatic feed

A method of advancing a workpiece into a machine with limited operator contact. Semi-automatic feeds are initiated by the machine operator.

sensing device

A mechanism that can detect the entry or presence of an operator in a hazardous area and shut down the machine. Sensing devices are designed, constructed, and arranged to create a sensing field or area and to deactivate the clutch control of the machine when the body part of an operator is within this field or area.


All the necessary preparation that occurs on a machine before an operation can be executed. Setup includes preparing and safeguarding machines, tools, and materials.

shear point

The area on a workpiece where a cutting tool cuts and separates the workpiece into smaller sections. Shear points are the first part of the tool to engage the workpiece.

shearing action

The force created by downward movement of an angled blade. Shearing action is used to remove metal.

special hand tool

A manual device that an operator uses to keep their hands away from hazardous areas. Special hand tools must be kept clean and sharp in order to avoid injury.


A machine component that holds and spins a workpiece or tool. Spindles should be well lubricated to prevent inconsistent motion that could damage the workpiece or tool.


An established policy regarding a particular practice or method. Standards created by the Occupational Safety and Health Administration (OSHA) are legally binding.

stored energy

Power that has not been used or dissipated. Stored energy can take many forms, such as unused electricity or tension in a spring.


A scissor-like device that allows operators to pick up parts from a slight distance. Tongs allow operators to pick up parts that would be hazardous to touch or place parts in hazardous areas such as a chemical bath.


A device on a machine that arranges multiple cutting tools in order and positions the tools for replacement. The toolchanger also stores the cutting tools between uses.

transversing motion

A form of straight-line movement. Transversing motion, such as with a belt or chain, can catch body parts, clothing, or hair.

trip wire

A touch-sensitive cable or wire that deactivates a machine when the operator applies pressure. Trip wires are located on the machine periphery so an operator can grab the device in order to stop the machine.

two-handed controls

A safeguarding machine start mechanism that requires simultaneous pressure on two separate controls to activate the machine or machine cycle. Two-handed controls allow operators to let go of the device once the machine or cycle begins.

two-handed device

A machine start safeguarding mechanism that requires both hands. Two-handed devices require simultaneous pressure on two separate controls to activate the machine or machine cycle.

type A gate

A moveable machine safeguarding barrier. Type A gates prevent operator access during the entire machine cycle.

type B gate

A moveable machine safeguarding barrier. Type B gates prevents operator access while the cutting tool enters the part but allows access as the tool exits the part.

work envelope

The defined area of space through which a robot can move. The work envelope, also known as the work cell, is dangerous for operators to enter unless the robot is powered down.

wrist device

Straps that connect the wrists of an operator to specific points on the machine. Wrist devices keep hands out of the point of operation.