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CNC Operator Interview

30 Questions and Answers by Rachelle Enns
Updated August 1st, 2020 | Rachelle is a job search expert, career coach, and headhunter
who helps everyone from students to fortune executives find success in their career.
Job Interviews     Careers     Technician    

Question 1 of 30

Talk to me about your mathematical skills, specifically in trigonometry, and how these skills will benefit you in this CNC Operator role.

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Talk to me about your mathematical skills, specifically in trigonometry, and how these skills will benefit you in this CNC Operator role.

In CNC machining, you will use trigonometry in numerous tasks and processes. Trigonometry and other math applications will help you to determine tool location, coordinate values, and solve complex equations.

Discuss any math-related coursework that you have, and be sure to highlight your greatest mathematical strengths. Perhaps you have post-secondary education on math-related topics. Maybe you excelled in advanced math when you were in high school. Whatever your background may consist of, show the interviewer that you have the math skills required to succeed in this CNC Operator role.

Rachelle's Answer

"As an experienced CNC Operator, I must understand the specifications of digital blueprints and mechanical drawings. I am well versed in applying trigonometric principles to determine coordinate values. I bring advanced skills in interpreting the symbolic language often included in engineer drawings and computer-generated 3D layouts. I am very familiar with Geometric Dimensioning and Tolerancing (GD&T), which I realize is a fundamental skill for success in this role. Every day in my current role, I apply advanced math concepts, specifically trigonometry, to calculate cutter or tool nose locations."


What is the primary function of Machine Control Unit (MCU)?

The interviewer is checking for your understanding of basic CNC Operator fundamentals. Essentially, Machine Control Unit (MCU) helps a CNC Operator to produce components by controlling a machine's motion. Many CNC Operators consider the MCU the core of a CNC system. An MCU receives the information it needs, processes that information, and then completes that step. Show the interviewer, in as simple terms as possible, that you understand MCU function and capabilities.

Rachelle's Answer

"The primary function of an MCU is to read the coding instructions, and to send correct instructions to each part of the machine as it recognizes and interprets axis transfer commands. An MCU is also used to support the axis movement controls and amplifier circuits for managing the axis tools. It holds the reviewed signals of location and velocity for each drive axis. It also executes auxiliary control purposes like coolant or tools. The MUC receives all the information as to what is required and then sends the information to the proper tools to follow through on the job. The MCU is the brain behind the machine functions."


Have you ever encountered an engineering design that you could not understand? If so, how did you overcome this obstacle?

Everybody faces obstacles in the workplace - that's just a fact of life! The interviewer wants to understand what steps you take when you face a puzzling situation. As a CNC Operator, you work in a highly technical field so, you must have the ability to problem-solve. Show the interviewer how far will you go to find the information you need, while also avoiding a productivity slump.

Since the question is 'Have you ever...' and 'How did you...' the interviewer is looking for a story-based example that showcases your work in action. Your response to this question is best delivered using the STAR framework. STAR is an acronym for Situation, Task, Action, Result. By forming your answer using this method, you will stay on track when telling your story, ensuring that you set the stage correctly - allowing the interviewer to follow along easily.

Rachelle's Answer

"(Situation) I am very experienced in reading mechanical blueprints and design; however, when working for Shop ABC, I came across a design where the directions were not completely clear. (Task) To avoid accidents or injury, I knew that I needed to understand the design completely before I started the work. (Action) First, I brought the design to my supervisor and asked her if she could help me to interpret the design. She's a whiz at blueprint reading, and even this one stumped her! Then, I asked a couple of senior colleagues for their interpretation as well. Last, I took our collective thoughts and went to a CNC online forum that I know and trust. (Result) It took some time, but after pulling these resources and collaborating as a team, we were able to crack the code. It felt great to have solved this problem."


Explain to me in simple terms - what is a vernier?

People often say that the better you understand a concept, the easier it should be for you to explain in simple terms. For this reason, the interviewer may ask you questions based on the fundamentals of CNC operations.

A vernier, in short, is a measuring tool used to measure parts of your work or a workpiece.

Take your existing knowledge of a vernier and explain it in simple, easy to understand terms. Imagine that you are describing a vernier to someone outside of your industry. How could you help them to understand?

Rachelle's Answer

"I find that I have a knack for explaining concepts to others. I believe in the adage that if you cannot explain a concept to a Grade 5 student, then you don't understand it well enough. If I were to explain what a vernier is, in its simplest terms, I would say that it's a tool used to measure the parts that I make on the job!"


What versions of CAM software do you know?

CAM is an acronym for Computer-Aided Manufacturing. Some individuals also refer to CAM as Computer-Aided Machining or Computer-Aided Modeling. CAM refers to the use of software to control machine tools. For this reason, CAM is used in CNC operations.

There are several versions of CAM software that you may know, depending on your level of experience with CAM and the focus of your work. Some popular CAM software options may include:

- HSMWorks
- LinuxCNC
- Aspire

The interviewer would like for you to discuss the software that you know, and your level of comfortability with each program that you mention. You could specify how much time you have invested in learning your leading CAM software or even talk about your experience training others on these programs.

Rachelle's Answer

"I am well versed in a variety of CAM programming and software including Mastercam, GibbsCAM and Siemens PLM Software. My strongest experience is with Mastercam, specifically with their mill and lathe solutions, from my experience at Company ABC. There, I used Mastercam for eight years. My secondary experience would be in GibbsCAM, as I worked with this software for around three years at Shop XYZ. I would rank my experience level in GibbsCAM as intermediate."


Approximately how many hours of experience do you have operating a CNC machine?

Depending on your region, the hiring company may require you to possess a particular number of hours as a machine operator before being hired. Offhand, you may not have this number locked down, and that is okay!

Think about the percentage of your career you have spent operating a CNC machine and give your answer. You can then calculate your hours by assessing the amount of time you have worked as a CNC Operator. For instance, if you have three years of full-time operator experience, you have likely worked 2,080 hours per year. This calculation would amount to 6,240 hours across three years. Then, if you believe that you spend 75% of your workday operating machinery, you could accurately say that you have spent approximately 4,680 hours operating machines.

Rachelle's Answer

"I have worked full time as a CNC Operator for five years, with about 3/4 of my days spent on various machines. So, rough calculations tell me that I spend about 6 hours per day operating a CNC machine. If I multiply this by 20 days per month, and 240 days per year, I estimate that I have spend around 1,440 hours per year operating a CNC machine. Over five years, that is over 7,000 hours. I am quite skilled when it comes to operating a CNC machine, and I look forward to putting in even more hours at your shop."


As a CNC Operator, what was the most challenging part you have ever created?

CNC Operators work hard to manufacture the machined parts that we use in our every day lives. Some of these parts are straightforward, and others are highly complex. Talk to the interviewer about the parts that you are accustomed to creating. Perhaps you received digital blueprints for a highly complex part that required a great deal of blueprint interpretation and calculations using trigonometry. What have you found to be the most challenging task in your machining career so far?

Discuss a situation that comes to mind and try to organize your response using the STAR framework. STAR is an acronym for Situation, Task, Action, Result. By delivering your story-based response using this method, you can easily organize your thoughts and give a compelling story.

Rachelle's Answer

"The toughest parts that I have created were surrounding aerospace components for the military when I worked as a CNC Operator for Company ABC. In that role, I faced added pressure for perfection, considering the nature of the parts. The parts we created were are much more complicated than one would think - not only because of the plans and precision but because of the materials we used, such as titanium and Kovar. In this role, I created parts such as miniature gears and sonic nozzles with precision venturis for flow measurement. These parts required skills in various micromachining techniques. Because of this experience, I feel well prepared to machine a multitude of complex parts."


Many companies are currently hiring CNC Operators. Why do you want to work for our company?

If there are numerous CNC Operator positions available in your area, the hiring authority may want to know precisely why you are interested in joining their company. To deliver a sincere and specific response, you will want to spend time understanding the role and researching their company. You will also want to put in the time to ensure that their company's purpose and the environment are a good match for you and your needs.

While your passion and excitement for the job are essential factors, it's always good to have some hard stats prepared. For instance, saying 'I have heard great things about your company, and I know I would be an excellent fit for this job,' is not very specific. Try to find some information related to the company's accomplishments. Mention specifically how those accomplishments made an impression on you.

- Research the company
- Highlight a unique talking point
- Show enthusiasm for the company's growth or recent efforts
- Discuss how the company's efforts and success tie to your career goals
- Mention how you will contribute, should you be hired

If you think you have the right response, ask yourself honestly if the answer can apply to any other company. If the answer is yes, it's time to get more specific.

It's important to note that 'Why do you want to work for our company?' is a question often confused with, 'Why should we hire you?' Be sure that you answer this question distinctly. Focus on your work-related passions, desires, and how the environment of the company, and growth opportunities they present, align well with your career goals.

Rachelle's Answer

"I want to work for your company for many reasons; however, the most personal and compelling include your safety record and the fact that I have two close friends who have worked here, and they have only positive things to say. I have spent a lot of time researching and getting to know your company, and I see that your safety record is unmatched. This partnership would be mutually beneficial in the sense that I put safety first in all that I do. I have a strong reputation as a seasoned CNC Operator who takes the time to care for my equipment. I also encourage my co-workers to take pride in their work by following best practices. Should you choose to hire me, I will make enthusiastic contributions to your productivity levels and will offer an unwavering commitment to safe work practices."


How comfortable are you with interpreting work orders, blueprints, engineering plans, and orthographic drawings?

A CNC Operator spends a great deal of their time reading digital blueprints, engineer designs, and other types of complex technical documents. The interviewer wants to understand your level of comfort with these tasks.

To express yourself, consider ranking your skills from beginner, intermediate, advanced, or expert. If you have any education in machine technology or computer technology, be sure to include details of your related training.

Rachelle's Answer

"I consider my knowledge in interpreting work orders, blueprints, and engineering plans to be at an advanced level. With around nine years of experience as a CNC Operator, I have a lot of exposure to these tasks. When I was completing my CNC Machine Operations degree, some of my education touched on orthographic drawings. I learned about constructing orthographic drawings, which I find to be very helpful knowledge now when I need to interpret them. Of course, there is always room for improvement, and I plan to be at an expert level in the next couple of years. I will achieve this goal by broadening my experience and taking online coursework related to more complex engineering plans and drawings."


Talk about a time when your good judgement saved your company from an accident or other costly incident.

The interviewer wants to hear a specific story-based example of a time when you were diligent and saved your company from a costly mistake. Perhaps you helped a co-worker to make the right decision when it came to a safety practice. Maybe your keen eye helped to you to troubleshoot a potential issue with a machine.

For this 'Talk about a time...' question, the interviewer is looking for a specific story-based example that highlights your good judgment in action. To deliver your story, try using the STAR framework, which is an acronym for Situation, Task, Action, Result.

Rachelle's Answer

"(Situation) When I was working as a CNC Operator for Shop ABC, my colleague noticed that his cutting machine was moving in the opposite direction of the origin. Thoroughly puzzled, he shut the machine down and was about to call the machine manufacturer to come and perform a service, but the company could not come for three days. (Task) It turns out, I had seen this issue in the past and was quite certain that I could fix the problem. (Action) I received approval from our supervisor to do some troubleshooting. After closer inspection, I found a broken origin switch, the proximity switch to be specific, and a short circuit in the switch coil. I recommended that we replace the switch coil. Our supervisor agreed, and we had the part replaced. (Result) The machine began working as expected! My knowledge and good judgment saved the company from a potential accident and a lot of machine downtime. My employer was very thankful for my diligence and machine knowledge."


How would you explain a micrometer to someone unfamiliar with our industry?

Many hiring authorities believe that the best way to gauge a candidate's understanding of a concept is to see how well they can teach it to someone new to the idea. How well do you know the fundamentals of the machining industry?

The interviewer would like to understand your level of knowledge when it comes to standard industry terms. The better you know a concept, the easier it should be for you to explain it in simple terms. You should have a clear response to this question, regardless of your level of experience as a CNC Operator. When it comes to the fundamentals of machine operations, what do you know, and how clearly can you explain?

Rachelle's Answer

"A micrometer is a tool used to measure tiny distances or thicknesses. A micrometer can deliver measurement accuracy as small as one-thousandth of an inch. Today, a CNC Operator can choose to use a traditional micrometer or a digital micrometer. Both options are highly accurate."

Anonymous Answer

"It is a measuring instrument."

Rachelle's Answer

You are correct! In the actual interview, as you know, you will want to expand on your response.

"A micrometer is a precision measuring instrument, great for fine measurements. Metric micrometers typically measure in 0.01mm increments."

Was this answer helpful? Yes or No


What motivated you to pursue a career as a CNC Operator?

The hiring manager wants to know that you are passionate about your line of work. You can answer this question in a more personal way, expressing what initially motivated you to pursue a career as a CNC Operator.

Perhaps someone in your family influenced you to work in the machining industry. Maybe you have always had an engineering type of mind, and you enjoy mathematical challenges and working in a hands-on environment. Whatever your motivators, give the hiring manager an engaging and meaningful response. Express what initially excited you to become a CNC Operator, and what factors continue to motivate you today.

Rachelle's Answer

"My interest in becoming a CNC Operator stems from when I began taking Software Engineering courses in University. I realized that I had a true knack for programming; however, I also knew that I wanted to work with my hands. These skills and interests are why I shifted to a career in machining and machine operating. I am pleased with my career choice and feel that it challenges me in a variety of areas such as mechanical troubleshooting, solving complex mathematical solutions, and interpreting engineering plans."


What programs have you used to document production and quality logs?

Proper (and clear) documentation of production and quality logs is a critical component to your success as a CNC Operator. For most roles, after you inspect your work for quality and accuracy, you will be expected to complete your production and quality logs. Speak to the interviewer about the fact that you are diligent with this task, well-organized, and compliant when it comes to completing your documentation clearly and on time.

If you have used production management software in the past, mention the one(s) with which you are most familiar. You may also bring experience with trusted pen-to-paper where you submit your logs physically without any program or digital system! Either way, express to the hiring manager that you are familiar with proper documentation and that you are ready and willing to comply with their company's documentation standards.

Rachelle's Answer

"When I first began my career as a CNC Operator, all documentation was on paper and pen! I would submit my logs in a book every day and then have the logs signed off each time I cleared a machine. Now, in my current position, we use an internal system for typing in and submitting logs. I prefer this system as it's more secure, and its on the cloud, so the operators can instantly share data with our supervisors. Rest assured, I am careful and diligent with my production and quality logs. I submit my work on time and as expected."


What challenges do you face most often in your current position?

Everyone has particular challenges that arise in the workplace. As a CNC Operator, some of your challenges might include poorly maintained machines, a coworker choosing the wrong cutting tools, programming errors, or even power supply problems.

This question is designed for the hiring manager to find out if you have a consistent struggle or challenge with specific aspects of your current job. They also want to gauge your problem-solving capabilities. When you answer this query, highlight the problems that you face in your current position while also discussing how you overcome these challenges. Be sure to keep your response as positive and proactive as possible. Avoid any negativity or rants about your workplace or coworkers.

Rachelle's Answer

"I enjoy working for my current employer; however, I find that the majority of my challenges are due to outdated equipment that causes numerous failures. As a result, I spend a lot of my time troubleshooting or repairing machines, and less time on the actual production process. I realize that the age and state of our equipment will not change, so I recently decided on a mindset shift. Now, rather than focusing on the fact that the equipment is unreliable, I focus on the fact that I learn something new every day when it comes to machinery troubleshooting and maintenance. Just this week, I learned how to fix a laser cutter when the trolly was not returning to the origin. I also fixed numerous light and light tube issues. All of these challenges are welcome because they mean that I will bring even more value to my next employer."


Have you ever made an error that cost your company a significant amount of money?

Mistakes happen on the job, and sometimes they can be costly to a company, whether that cost is financial or time-related. What the interviewer wants to know is that you own up to any errors that you may make in the workplace. It's essential to show the hiring manager that you take accountability for your actions.

Think of a time when you made an error in the workplace. Discuss the situation, the steps that you chose to overcome the issue, and then the resolution.

If you have never made a costly mistake in the workplace: Rather than staying that you do not make mistakes, you can discuss a minor issue. Or, give a hypothetical example and explain how you would react if you found yourself in that situation.

Rachelle's Answer

"Earlier in my career, I was working on an older style laser cutter and was working too quickly. The machine shorted, and we couldn't get it up and running again. I apologized profusely to my supervisor. Knowing that I owned the mistake and didn't make an excuse was enough for my manager to forget it ever happened. I was sure to be extra cautious after that."

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