Estimated reading time: 10 minutes
Safety guarding on milling machines is more important than ever due to occupational health and safety evolution. Milling machines have existed for centuries and are still vital to today’s manufacturing industry. Early milling machines did not have operator safety in mind and featured open drivetrain components and no safety shields.
As with any powered machinery, it’s essential to ensure that you safeguard your milling machine appropriately to prevent accidents and injuries. This article will discuss how to safeguard a milling machine and the different types of safety guarding and shields you can use. But first, knowing what a milling machine does and how it operates is vital to safeguard these machines adequately. Are you already familiar with milling machines? You can jump to milling machine guarding here.
What’s a Milling Machine & What Does It Do?
A milling machine is a tool that cuts and shapes materials like metal or wood. It uses spinning blades to remove material from a piece, creating flat surfaces or complex shapes. A vise or table secures the part to shape, and the workpiece moves against a cutter to make precision cuts.
A Brief History of Milling Machines
In the early 19th century, inventors created the first milling machines. The initial purpose of the milling machine was to make interchangeable parts for military firearms. Later, workers used these machines to produce parts for other industries, such as automotive and aerospace.
Types of Milling Machines
There are several types of milling machines, each designed for specific purposes and applications. Here are some of the most common types:
- Vertical milling machine: This machine has a vertical orientation of the spindle axis, and the cutting tool is upright. These are the most popular milling machine type. I recommend the following guarding for these: Standard Milling Machine Shield w/ Interlock
- Horizontal milling machine: The spindle axis is horizontal in this type of machine. This machine is best for cutting large and heavy pieces of metal. Companies often use it for making automotive parts, marine equipment, and industrial machinery.
- Universal milling machines can do both vertical and horizontal milling operations. It may have a swiveling head that rotates to various angles. I recommend the following shield for these: Universal Milling Machine Guarding w/ Flat Shield
- CNC milling machine: Operators control this machine with a computer and screen, capable of performing precise and complex milling operations. Some older CNC machines don’t have the necessary guarding in place and may need custom upgrades such as this: Model-TA-MM
- Bed-type milling machine: This machine has a large bed that supports the workpiece, and the cutting tool is held in a fixed position. It is a heavy-duty machine that is best for cutting large, heavy workpieces. The safety guarding for the Universal milling machine will work for these or a sliding shield like this one: Model PR
- Gantry-type milling machine: This machine has a bridge-like structure that spans over the workpiece, and the cutting tool is held vertically. It is used for cutting large and heavy pieces of metal. It is often used in the aerospace and automotive industries. We have safeguarded many of these types of milling machines with custom upgrades.
Each type of milling machine listed above will require its specific safety guarding and solutions. For example, a CNC machine usually has a completely enclosed enclosure. In contrast, a manual vertical milling machine may have only a chip shield.
Milling Machine Safety Guarding
Milling machines can be dangerous if one does not take proper safety precautions. The cutting tools on a milling machine are sharp and can cause severe injuries if they meet skin or clothing. The machine’s moving parts, such as the spindle and table, can cause crushing, pinching, or entanglement injuries.
However, operators can use milling machines safely with the proper training, knowledge, and safety equipment. Safeguards like barriers, shields, and emergency stop buttons should be in place and functioning correctly to prevent accidents and protect operators and bystanders from harm.
A shield on a milling machine can protect the operator by preventing flying debris, coolant, or chips from hitting the operator’s face, eyes, or body. The shield is typically made of durable material, such as polycarbonate or tempered glass. It is positioned between the cutting tool and the operator. The guard can be adjusted to the appropriate height and angle to provide maximum protection while allowing the operator to see the cutting process.
In addition to protecting the operator from debris, a shield can help prevent accidental contact with the rotating cutting tool. Suppose the operator accidentally touches the cutting tool while it is spinning. In that case, the shield can help prevent the operator’s hand or fingers from contacting the tooling, potentially preventing a severe injury.
Real Stats
In 2018, 58% of work-related amputations involved machinery such as milling machines. Of all amputations in the same year, 1,660 cases involved machinery used for metal, woodworking, or unique materials.
“Amputations occur most often when workers operate unguarded or inadequately safeguarded mechanical power presses, power press brakes, powered and non-powered conveyors, printing presses, roll-forming and roll bending machines, food slicers, meat grinders, meat-
cutting band saws, drill presses, and milling machines as well as shears, grinders, and slitters.”
–Osha Amputation Factsheet
Safety Guarding on Milling Machines: Don’t Forget the Back & Sides!
Safeguarding the back and sides of a milling machine is essential to protect anyone near the device. The operator does not necessarily have visibility, and walkways may be in line with projection hazards. A great way to safeguard these areas is to put movable barriers or fencing and protect passers-by from flying chips and accidental contact.
Take Note! Watch out for the moving table on a milling machine. Ensure walls, barriers, or forklifts aren’t too close to a moving table. Do not install an immovable fence too close to the table because it could cause a crushing or pinch zone.
Cover The Drawbar
Remember that safeguarding is prevention, and we can’t always think of all the ways an accident can happen. Often overlooked as a source of safety hazards, the drawbar is a component of a milling machine that rotates at high speed and is frequently exposed. Even though the drawbar may not be easily accessible, covering the spinning drawbar can prevent accidental entanglement hazards.
Do you have a power drawbar? A power drawbar will already be a safeguard because they cover the drawbar. Before performing maintenance on these, ensure you turn off any compressed air.
In the photo beside, you can see Ferndale Safety’s solution for covering milling machine drawbars. For more information, click here.
Know How to Stop Your Machine
Many states and countries have regulations and standards that require the control buttons to be within easy reach.
For example, Minnesota rule 5205.0865 states: “On machines with points of operation, pinch points, or nip points, each machine shall be equipped so the operator can cut off the power to each machine without leaving the position at the point of operation.”
On a milling machine, this would mean avoiding having any start/stop controls on the back or sides and instead having it within arm’s reach of the point of operation.
What is the “point of operation” of a milling machine?
The point of operation on a milling machine is defined as the point or area where the tool’s cutting edge is in contact with the workpiece. This is where the spindle and tool rotate, chips & coolant are thrown, and heat is generated.
The E-Stop Button
Even though an emergency stop button is not always required, I recommend adding it. Adding this button is inexpensive and universally recognized as a way to stop a machine. Remember that not everyone knows how to stop a machine; a random person may need to shut the machine down in an emergency.
General Safety Guidelines
It is essential to know the potential hazards of working with milling machines. To avoid accidents, it is crucial always to maintain focus on the work and eliminate any potential distractions before beginning machining. However, distractions can happen, and safety guards and shields can prevent accidental injury.
Injuries: Anyone Can Get Distracted
A seasoned employee was preparing to resurface the underside of an engine valve cover. He used a fly cutter on his milling machine, a task he had executed proficiently throughout his twenty-year career. However, his focus was interrupted by a loud noise behind him. He looked away just as he was about to secure the bar inside the cutter’s body. When he returned, he inadvertently overlooked that the bar was not securely tightened and proceeded to turn on the milling machine. Consequently, the bar was hurled at a high velocity toward his chest, resulting in severe injuries and extensive hospitalization. A safety shield at the point of operation could have potentially absorbed most of the impact and prevented the employee from getting hurt.
In addition, it is essential to develop safe working habits, such as using safety glasses, proper setups, and appropriate tools. By taking these precautions, operators can help ensure their safety while using the vertical mill.
- Use safety glasses, hearing protection, and appropriate safety footwear.
- You must never wear rings and jewelry; tie back long or loose hair.
- Wear close-fitting clothing and never wear gloves while using a milling machine.
- Ensure the floor around the milling machine is not slippery. Use non-slip anti-fatigue mats whenever possible.
- Never try to stop or brake rotation with your hands.
Potential Hazards on a Milling Machine
- Contact with rotating parts: The rotating cutting tool, spindle, and workpiece can all pose a risk of injury if an operator’s hands and fingers. Clothing can become entangled.
- Flying debris: Chips, coolant, and other debris can be thrown from the cutting tool during operation, potentially causing eye or skin injuries. Unsecured workpieces could be thrown from the point of operation.
- Noise: Milling machines can generate high levels of noise that can cause hearing damage if proper hearing protection is not used.
- Burns: Steel chips can reach high temperatures and cause burns.
- Electrical hazards: Sharp chips and swarf can cut through power cords and conduits over time. Periodically inspect your machine’s electrical system and replace any damaged cables.
- Pinch points: The machine’s moving parts, such as the table and spindle, can create pinch points that can cause crush injuries if not properly guarded.
References:
- OSHA 29 CFR 1910.212 – Covers the general requirements for machine guarding
- OSHA 29 CFR 1910.132(a) – Splashes from coolant can present a skin irritation hazard.
- OSHA 29 CFR 1910.133(a)(1) – The shield or guard must supply complete eye or face protection.
- OSHA 29 CFR 1910.212(a)(3)(iii) – Removal of chips using tools and not your bare hands.
- ANSI B11.8-1983 – “Safety Requirements for the Construction, Care, and Use of Drilling, Milling, and Boring Machines.”
- ANSI B11.8-2021 – “Safety Requirements for Milling, Drilling, and Boring Machines with or Without Automatic Control”
- CPL 03-00-022 – “National Emphasis Program on Amputations in Manufacturing Industries,” Federal Directive dated 2019-12-10.
- ISO 16090-1:2017 – Machine tools safety — Machining centers, Milling machines, Transfer machines — Part 1: Safety requirements
Bibliography:
- Woodbury, Robert S. History of the Milling Machine. In Studies in the History of Machine Tools, MIT Press, ISBN 978-0-262-73033-4, 1972.
- Bureau of Labor Statistics, U.S. Department of Labor, The Economics Daily, Machinery involved in 58 percent of work-related amputations in 2018 at https://www.bls.gov/opub/ted/2020/machinery-involved-in-58-percent-of-work-related-amputations-in-2018.htm (visited April 6, 2023).
- Occupational Safety and Health Administration, U.S. Department of Labor, OSHA Fact Sheet at https://www.osha.gov/sites/default/files/publications/amputation-factsheet.pdf (visited April 3, 2023)
- Wikipedia contributors. (2023). Milling (machining). Wikipedia. https://en.wikipedia.org/wiki/Milling_(machining)
