Episode 28 – Machine Guarding


Toolbox Topic: Machine Guarding

Machine guarding is essential. In this episode, we will discuss guarding requirements, different types of guards, and the dangers of unguarded equipment.



According to OSHA 1910.212(a)(1), Types of guarding: One or more methods of machine guarding must be provided to protect the operator and other employees in the machine area from hazards such as those created by point of operation, ingoing nip points, rotating parts, flying chips, and sparks.

A machine is a physical system using power to apply force and control movement to perform an action. Humans often work with machines to increase their productivity.

A machine guard is a device or barrier. Its purpose is to protect humans from an injury caused by the point of operation, power transmission, or moving parts of machines. Injuries can include amputations, lacerations, burns, eye injuries, and crushing injuries.


History of Machines

Some consider the hand ax to be one of the first machines. An ax is a wedge. When put into motion by human power, lateral force converts to transverse splitting force.


The Six Simple Machines

A wedge is the oldest of the six classic simple machines. The other five simple machines include the inclined plane, the wheel and the axle, the lever, the pulley, and the screw. Almost all other machines are based on these six simple machines.


The Egyptians

The Egyptians discovered two of the six simple machines which enabled them to build the pyramids. As we discussed in the safe lifting episode, the Egyptians used the inclined plane and the lever. The inclined plane was used to move rocks to higher positions. Moving something up a ramp instead of lifting it straight up required less force, but it took more time. A lever is a simple crane and works on the same principle as a seesaw. A lever is pulled down on one end to lift the load and then pulled left or right to move the load to its desired location.


The Greeks and Greek Philosopher Archimedes

In the 3rd century BC, the Greek philosopher Archimedes described three of these simple machines, the lever, pulley, and screw. He discovered the principle of mechanical advantage. The Greeks eventually discovered five of the six simple machines; even so, their knowledge was limited to the basic concepts of classical mechanics.


The Renaissance

During the Renaissance, it was the scientist Galileo that first understood that simple machines do not create energy. They simply transform it.

Leonardo da Vinci discovered the classic rules of sliding friction in machines sometime in the mid-15th or early 16th century; However, it remained unpublished in his notebooks.


Industrial Revolution

The Industrial Revolution spawned vast improvements in machine technology that changed the world. Consequently, the technologies that were developed would affect nearly every facet of human life for centuries.

It changed everything from transportation, agriculture, and manufacturing, to heavy industry.

It transformed industries that had relied on simple machines and animal labor into full-fledged mechanized systems and brought humans into the modern age. With the introduction of electric motors, and engines powered by steam or fossil fuels, machines rapidly grew in complexity, ability, and productivity.


Machine Guarding Statistics

According to OSHA, there are still employees who are exposed to unguarded or inadequately guarded machines. So, workers who operate and maintain machinery suffer approximately 18,000 amputations, lacerations, crushing injuries, abrasions, and over 800 deaths per year.

A 2005 U.S. Bureau of Labor survey indicated 8,450 non-fatal amputation cases. These injuries result from the use and care of machines such as:

  • saws
  • presses
  • conveyors
  • bending, rolling, or shaping machines
  • powered and non-powered hand tools
  • forklifts
  • doors
  • trash compactors
  • other material handling activities

Approximately forty-four percent (44%) of all workplace amputations occurred in the manufacturing sector, and the rest happened across the agriculture, wholesale, construction, retail trade, and service industries.


Machine Guarding Safety Tips

**Safety Tip#1 Be aware of a Machine’s Hazardous Parts

Machines have three danger areas: the point of operation, the power transmission apparatus, and its moving parts. Each of these components can be dangerous and need safeguarding:

The Point of Operation: The area of the Machine where you perform work is the point of operation.

Power Transmission Apparatus: the part of the mechanical system which transmits energy to the part of the machine performing the work.

Moving parts: The parts of the Machine that move while the Machine is running


Tip#2 Know the Types of Mechanical Motion that Must be Guarded

  • Pinch Points: Points where body parts can get caught between moving parts or between moving and stationary parts.
  • Rotating: The circular motion of shafts that stick out or protrude can pull clothing, jewelry, or body parts into the point of operation.
  • Reciprocating: An Up-and-Down or back-and-forth motion that can strike an employee or trap them between the moving object and a fixed object.
  • Traversing: Continuous movement in a straight line that could strike or catch an employee in a pinch or shear point between a moving and fixed object.
  • Cutting: Action of drilling, sawing, boring, milling, or slicing.
  • Punching: The action resulting from a machine that moves a slide (or ram) to stamp a sheet metal or other material.
  • Shearing: When a powered slide or knife trims or cuts metal, paper, or other materials.
  • Bending: When force is applied to form bends in metal or other materials.


Tip#3 Machine Guarding Requirements

Install and maintain guards to meet these minimum requirements, including:

  • No interference: A guard should not impede an operator from performing the job.
  • Allow Safe Lubrication: The Machine should be able to be lubricated without removing the guards.
  • Prevent Contact: The guard should prohibit the operator (or anyone) from placing body parts near dangerous moving parts.
  • Secure: Install guards, so they are not easily removed or tampered with.
  • Protect from Falling items: The guard should protect the Machine so that objects cannot fall into it while operating.


Tip#4 Four Types of Guards

There are four types of machine guards:

  • Fixed Guard – It is the preferred guard because it is simple to use and very difficult to remove.
  • Interlocking Guard – It automatically disengages or shuts down the machine if the guard is opened or removed. The machine remains inoperable until the guard is back in place.
  • Self-Adjusting Guard – It allows a barrier to open and close depending on the size and movement of the material. The guard moves as the material moves into the danger zone, creating an opening only large enough to accommodate the material.
  • Adjustable Guard – It will adjust to allow for various sizes of material. However, it opens up the potential for human error and accidents.


Tip#5 Never, Ever Remove Guards

This is something I have never understood. The guard is there to make sure you don’t lose any of your digits. 1st, Don’t ever remove them! Before you work with any equipment, inspect it. If the guard is missing, lock out and tag out. Lastly, alert a member of management.










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