It’s easy to overlook safety operations for CNC machines, but safety managers and industrial hygienists should better understand the nuances of their operations and maintenance to keep workers protected.

Just because computer numerical control machines are programmable doesn’t mean they cannot hurt an operator or cause damage to your plant or other people standing nearby.

For one thing, if a part is not programmed correctly, the machine may crash, damaging the part, tools, spindles and other equipment inside the hood. Modern CNC machines protect operators and bystanders from flying metal chips or broken tools with safety interlocks that don’t allow the door to be opened until all motion has stopped.

“Unfortunately, on some of the older machines, you can manually override the locks with the machine still running,” says Frank Quarato, president of the Center for Safety & Environmental Management. “If you open the door while the machine’s running, you’ll have all the physical hazards that you can think of … The machines don’t slow down—they don’t even know you’re there.”

OSHA Regulation: CNC Machine Safety Requirements

The Occupational Safety and Health Administration requires employers to keep the workplace free of serious hazards, such as exposure to moving machine parts that could crush or amputate fingers or hands. In 2013, manufacturers reported 2,000 workers suffered amputations. The rate of amputations in the manufacturing sector was more than twice as much (1.7 per 10,000 full-time employees) as that of all private industry (0.7), according to Bureau of Labor Statistics data reported by OSHA when the regulatory body updated its National Emphasis Program on Amputations.

According to OSHA, “any machine part, function, or process that may cause injury must be safeguarded.” These safeguards could come in the form of engineering controls, which are designed as an integral part of the machine and don’t depend on employee decision-making or behavior.

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Tip #1: Workplace Safety vs. Quality Assurance: Keep CNC Machine Doors Closed

Machine controls may include safety interlocks, but if the equipment does not come with them, other protections must be put in place. This protection could include temporary barriers and warning signs, along with operator training.

“Catastrophic accidents can happen to inexperienced CNC machine operators who don’t understand the danger of opening the hood before the machine has completely stopped, as well as to those who purposefully break the rules,” Quarato says.

For example, operators should never place any body part into the machine or near the spindle while attempting a power-up mode.

“Don’t put one hand on the emergency stop button and reach in with the other hand to start turning machine parts,” he says. “By the time you slap that stop button, the centrifugal force alone could suck you in the machine.”

How does an operator know when a cycle is complete and it is safe to open the compartment?

“Every CNC machine has a home position where it returns before starting another cycle, and operators need to learn what that is,” Quarato says. “Always allow it to return home and power off before reaching into the machine or into any of the actionable areas.”

Even with safety training, “some operators feel if they can keep the door open to watch the part while the machine is running, that would be better for quality assurance, but nothing could be further from the truth,” Quarato says.

“Even if the part doesn’t fall off the spindle onto your foot, you may very well get hit with a chip from a tool, or the stock itself,” he says.

For true quality control, Quarato says, operators should review and dry run all new programming—without stock or tooling.

“In some cases, CNC machines have graphic displays that illuminate the toolpath so you know where that tool’s going to go and you can predict it because you’ve seen it run once already,” he says.

“Every CNC machine has a home position where it returns before starting another cycle, and operators need to learn what that is… Always allow it to return home and power off before reaching into the machine or into any of the actionable areas.”
Frank Quarato
President, Center for Safety & Environmental Management

Tip #2: Employee Safety vs. Tooling Costs: Don’t Alter CNC Machine Tools

“Some cutting tools are very expensive, and operators know that if they use a cheaper tool, they can save a little money,” Quarato says. 

“But all CNC operator’s manuals warn against altering the tooling or working outside the programmatic functions of the machine,” he says. “Alterations of any kind can cause incredible energy to be released if hardened steel tooling collides with other equipment, and it can literally cause tools to break through the enclosures, creating a safety hazard.”

Only qualified operators should be operating a CNC machine, Quarato says, but too much automation allows employers to hire minimally skilled workers to perform the most difficult tasks. The bigger the gap between what the machine can do and the operator’s knowledge, the more likely that the operator can get himself and those around him in trouble.

Tip #3: Clean and Maintain Your CNC Machines to Reduce Cuts and Burns

Most employers know having a clean machine will not only protect and extend the life of the machine, but also produce higher quality parts. At the same time, housekeeping and total clean machine policies are mandatory for safe operations of CNC machines, according to Quarato.

“The machines have sprayers that spray the part down with lubricants during operations, and if chips build up and block that spray pattern, it can cause the tempered tools to get hot and changes their chipmaking abilities,” he says. “This can cause your turnings and chips to get so hot, they can cut and burn you.”

Tip #4: Use the Proper PPE for Eyes, Ears, Hands, Feet and Faces

In addition to specific safety training for CNC machines, employers are required to provide equipment and training to meet the OSHA standard for noise protection and other personal protective equipment, including eye and face, foot and hand protection.

“While most CNC machines have good enclosure, wearing safety glasses, hearing protection and appropriate foot protection is always recommended to protect from things that might fly out or be dropped out of the machine once the part is done,” Quarato says.

“Technology is changing all the time and older operators already know the most basic machining skills, such as waiting until the machine stops spinning and returns to home position, but younger ones don’t,” Quarato says.

“Too often today’s employees think that the machine knows what it’s doing, so if it looks like it’s done, even if it hasn’t returned home, they reach in there when the machine still has a couple of operations left,” he says. “It’s like reaching into a washing machine when you thought the spin cycle was done, but it had one more cycle to go.”

For more on how to safely operate a CNC machine while maximizing output and reducing waste, see the ANSI report “ANSI B11.TR7-2007 (R2017) Designing for Safety and Lean Manufacturing” (purchase required).

How do you ensure your team is properly trained on CNC machine safety?

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I am employee at a general motors facility ,they have mandated now to where KEVLAR saftey sleeves upon entry to the plant. I have no problem with that, I am a TOOL AND DIE MAKER running turning spindled machinery ( CNC mills, DRILL PRESSES ,LATHS ) and they tell us to take out our thumbs out of the thumb holes in the sleeves while operation . I have seen hands ripped off over the 43 yrs in this trade because of loose clothing and long sleeves. Can you give me an address for an OSHA regulation or office to contact? our Union has been not to cooperative and I feel our safety has not been their greatest concern.
Bernd Loos


Hi Bernd, Thanks for reaching out on the Better MRO site. Below are links to the Federal OSHA website, which will also have contact information. Your state may have its own branch of OSHA, so be sure to check that. I've also included references to the requirement on long sleeves, loose fitting apparel etc... OSHA website: Loose clothing in OSHA articles: It is important to note that protective clothing and equipment can create hazards. A protective glove which can become caught between rotating parts, or a respirator facepiece which hinders the wearer's vision, for example, require alertness and continued attentiveness whenever they are used. Other parts of the worker's clothing may present additional safety hazards. For example, loose-fitting shirts might possibly become entangled in rotating spindles or other kinds of moving machinery. Jewelry, such as bracelets and rings, can catch on machine parts or stock and lead to serious injury by pulling a hand into the danger area.


I've been thinking about learning how to use a CNC machine. It's good to know that you need to always keep the doors closed on the machine, like you said. I'll definitely have to keep that in mind. I would hate to end up having an accident while using the machine.


I almost forgot about OSHA regulations! That is so important to remember! I will have to make sure the shop is up to code.


Let’s not forget to check the program you are using. Changing fixtures and forgetting to change programs will have a negative affect.


Thanks for the tip, Robert. And thank you for visiting Better MRO.


Great article. while working on CNC, we engaged so much sometimes that we take safety for granted. Even I have a CNC machine shop ( ) where we manufactured CNC custom machining parts. The process involves a dedicatedly working on machines and then safety plays an important role. I would appreciate your effort for sharing this article.


Thank you, Norm, for sharing your experience and for your commitment to safety!


My husband worked for Robert Bosch Company for 20 years before factory closed in the area we live. He operated the CNC machine (along with several others machines) for this GM Truck Rotor factory. He breathed "fine metal" particles for years at this job. Wasn't told until years later to use the respiratory to help avoid the tiny particles. He passed away 4 years ago "due to cancer" ..Colon. Do you know any site I can go to regarding cancer in the auto industry ?? Thanking you in advance.


We're sorry to hear about your husband Brenda. We don't have expertise in the medical field, and we certainly wouldn't want to point you in the wrong direction. Does anyone have info for Brenda they can share?


It's good to know that you shouldn't open the hood before the machine is done. My husabnd was telling me last night about how he wants to get a CNC machine for his company in a couple of weeks, but for now, he will have to go to a professional to help him with it. I'll make sure to pass this information along to him once he does get a CNC machine so that he can know how to stay safe.


To who may concern, I am a newbie in this CNC machine, and I have thought or question regarding the ways of using this machine and also the operation.

-I wonder what will be the impact on the workpiece if the clamping force on the part is too high in the CNC machining process. 

-What's the consequence if the workpiece is held by hand instead of using the fixture while performing CNC drilling. 


-Predict the impact when an improper drill is used to drill a hole in CNC Machining.

-What are the possible reasons that caused chipping to occur?


Hi Jason, deformation would occur on a thin workpiece made of certain materials, if high clamping forces were applied. Upon inspection, when the clamping forces are released, you would most likely find your part out of tolerance.

The consequences of holding a part by hand for a CNC drilling application, would prove devastating.  There must be a workholding solution that could be utilized. Please call (800) 645-7270 and ask to speak to a member of the MSC Metalworking Tech Team.

Regarding the inquiry on using the improper drill –  more information is required to form a recommendation for you.  Again, please call & ask for the metalworking tech team.

There are many factors that would cause chipping – what is the material & hardness of the part you are working on?  Is this a HSS, cobalt, or carbide drill.  Are you running with coolant?

The MSC metalworking tech team can help you with applications and inquiries from the mats you stand to the lights overhead. Please give us a call 07:00 am ET to 08:00 pm ET.


It's good to know that CNC machines are being made today to protect operators and bystanders from flying debris. I think this a great idea because I can only imagine how dangerous the machines are. I would like to get one of the newer CNC machines and use it because it will keep me safe.


This is a wonderful article stating about the 4 essential workplace safety tipsbcnc machinists This article is attracting mostly everyone in the world. Such illustration that anyone can understand it easily and I am sure many people will come to read this in future.

CNC machine shop


Great Article by Author, We have products for CNC machine safety HERE


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great article. 

As a question is it normal for a operator to leave

a machine while the in operation. 


It's interesting to know that there are OSHA regulations to remember when it comes to CNC machining. I'm considering to get free CNC training courses soon because I've been taking up carpentry as a hobby for the past two years. Expanding my horizons would help me expand my skillset.


Thanks for the excellent guide to various parts of a CNC machine. I am sure many people will have some idea about the process after viewing your past. Keep up the good work of raising people’s awareness.


Thank you for your artical and all the info, all your knowledge can only make hundreds of operaters safer!


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