A candidate speaks confidently about Fanuc, G-code, and measuring tools during an interview. Once in the shop, it becomes clear that they ran prepared programs but never set tools or inspected the first part independently. The systems listed on the resume were familiar to them; the scope of their own work was less clear.
Employers can reduce this uncertainty by looking for evidence of specific tasks. The relevant tasks differ for an operator, a setup technician, and a CAM programmer, even when all three have worked with CNC machines. Start by defining the work attached to the vacancy. Then ask candidates to explain or perform a small, representative part of it.
Define the boundaries of the job
An operator may load a program and stock, monitor the cycle, and measure finished parts. A setup technician prepares the workholding, sets tools, enters offsets, and brings the first part into specification. A CAM programmer plans the process, creates toolpaths, and posts the NC program. Duties can overlap in a particular shop, so a job title cannot stand in for an actual task list.
NIMS describes operator and CAM programmer roles separately in its machining standards. That is a useful starting point for an assessment: test the work the new employee will really do. If the shop intends to train a new hire on a particular control, there is little reason to make knowledge of every menu an entry requirement.
Ask about work the candidate actually did
Instead of asking for a general account of experience, have the candidate walk through one familiar part. Which machine was used? Who chose the datums and tools? Which dimensions were checked after the first pass? What did the candidate change personally, and what did they hand over to the process engineer or setup technician? The answers help distinguish individual work from the output of a whole shift.
Material from previous jobs can support the discussion: a part photograph, an anonymized setup sheet, inspection results, or a program the candidate is allowed to share. The employer should be able to connect each item to the person's contribution. A photograph of a complex part alone cannot show who programmed it, set the machine, or checked its dimensions.
Files from a previous employer may be confidential. An oral walkthrough or an exercise based on a neutral part supplied by the hiring shop can serve the same purpose. A candidate's lack of a portfolio should not automatically count against their skills.
A short work sample
The U.S. Office of Personnel Management, or OPM, describes work samples as tasks that resemble the duties of the job. For a CNC opening, the sample can cover a small piece of ordinary production work. There is no need to ask every candidate to manufacture a complete part.
For an operator, provide a drawing and a set of measurements. Ask which dimensions are out of tolerance and what they would do before the next part. For a setup technician, provide a setup sketch and tool list, then ask how they would establish datums, check tool projection, and approach the first run. For a CAM programmer, use a simple model and ask for an operation sequence, datum choices, and the points where toolpath and postprocessor checks will be needed.
Any exercise on a live machine should follow the shop's normal safety procedures under the supervision of a responsible employee. Many skills can be assessed from a drawing, a program excerpt, a simulation, or a discussion of a typical fault. Tell candidates in advance how long the exercise will take and what will be assessed.
Use the same criteria for each candidate
A work sample is easier to use when the result can be compared consistently. Before the interview, write down a few criteria: did the candidate read the tolerance correctly, notice a collision risk, propose a sensible check sequence, and explain when to seek approval? The criteria should fit the position. An operator should not have to develop a CAM strategy if that is outside the job.
Ask all candidates the same core interview questions and score their answers against a prepared scale. OPM calls this a structured interview. Follow-up questions can clarify an answer, but each candidate should face the same basic assessment.
Record observed actions. For example, a candidate identified an out-of-tolerance dimension and proposed stopping production until the offset was checked. That note gives the hiring team something concrete to discuss. A general positive impression says little about which tasks the person can perform independently.
No short exercise can reproduce an entire shift. A discussion of past work, a focused work sample, and consistent scoring can still give the employer a clearer picture of practical ability. The same criteria can then guide onboarding: which operations the new hire can take on immediately, and where training or a supervisor's check is needed.