Instrument Machinist
Posted Apr 1, 2026 · We last checked this listing on Oct 6, 2026
Likely interview questions for this role
Written from this job description, not a generic list. Each one notes what the interviewer is really checking.
About your past
Tell me about a part you scrapped. What went wrong and what did you change afterward?
What they are checking: Whether they own mistakes and learn from them rather than blaming the drawing or the machine.
Tell me about a time you had to balance cost and quality on a job.
What they are checking: Whether they can make parts that meet the design at a reasonable cost instead of over-finishing everything.
How do you keep yourself and others safe in a shared machine shop?
What they are checking: Whether they follow and model shop safety habits consistently, not just when someone is watching.
What would you do
A scientist hands you a rough sketch and says they need a part by Friday. What do you do before you start?
What they are checking: Whether they clarify material, critical features and tolerances up front instead of guessing on a one-off research part.
You notice a drawing has a dimension that looks wrong or a feature that can't be made as drawn. What do you do?
What they are checking: Whether they stop and check with the customer or foreman instead of making it wrong or changing it on their own.
About the work
Walk me through how you plan the machining sequence for a part from a blueprint you have never seen before.
What they are checking: Whether they think about setups, datums and order of operations before cutting, which saves scrap and time.
How do you hold a tolerance of plus or minus half a thousandth on a manual machine?
What they are checking: Whether they understand heat, tool wear, rigidity and measurement well enough to hit tight tolerances repeatably.
What materials have you machined beyond steel and aluminum, and what did you have to adjust for each?
What they are checking: Whether they can handle materials like stainless, copper, titanium or plastics common in lab instruments.
How do you inspect your own work before handing a part over? Which instruments do you use?
What they are checking: Whether they measure carefully with micrometers, indicators and gauges rather than trusting the machine dial.
What routine maintenance do you do on your machines, and why does it matter for accuracy?
What they are checking: Whether they see machine care as part of the job, since a neglected lathe cannot hold tolerance.
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Practice this out loudThe full job description
As published by Fermilab.