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Machinist interview questions and how to answer them

A machinist interview is mostly a foreman trying to find out whether you've actually stood at a lathe or just read about one. Expect questions about manual work, print reading, and how you handle a part you only get one shot at. Answer with specific jobs you've done, the machine you did them on, and what you'd do differently now.

12 questions8 minute read

Part 1

1.Walk me through single-point threading on a manual lathe.

Why they ask

It's a quick way to tell a real manual machinist from someone who's only run CNC. The steps are specific, and people who haven't done it tend to get vague fast.

How to answer

  • Set up the quick-change gearbox for the pitch and set the compound over to the right angle
  • Grind or pick the threading tool and square it to the work with a center gauge
  • Use the thread dial to engage the half-nut at the same point every pass
  • Take lighter passes as you go deeper and check with a thread gauge or the mating part
  • Mention how you handle a thread that has to stop at a shoulder

2.A customer brings in a worn part with no drawing. How do you make a new one?

Why they ask

Repair and reverse engineering work is a big share of what general machinists do. They want to know if you think about what the part does, not just what it measures.

How to answer

  • Measure every feature and sketch it with dimensions before touching material
  • Ask what the part mates with and which surfaces take wear
  • Size worn surfaces back to what they likely were, and confirm with the customer when you're unsure
  • Check the material, by asking, by spark test, or by the look of the chip
  • Write up what you made so the next one is faster

3.How do you indicate a part in a four-jaw chuck?

Why they ask

Four-jaw work is where patience shows. It's also a basic skill the foreman will expect you to have without training.

How to answer

  • Rough it in close by eye or with the chuck face rings
  • Set a dial test indicator on the diameter and rotate by hand
  • Loosen the low side and tighten the high side, working opposite jaws in pairs
  • Check again after snugging all four jaws, since tightening moves it
  • Say how close you'd get it for the job in front of you
4.You're making one part with a tight bearing fit. How do you make sure you hit it?

Why they ask

On a one-off there's no second piece to adjust on. They want to hear how you control risk when a mistake means scrap.

How to answer

  • Rough to size and leave a small amount for finish passes
  • Let the part cool before the final cut if it's been getting warm
  • Take a spring pass and measure after every cut near size
  • Check the micrometer against a standard before trusting it
  • Use the mating bearing or a gauge to confirm the fit when you can
5.When would you make a part on a manual machine instead of the CNC?

Why they ask

A general machinist is expected to pick the right machine for the job. This shows whether you think about time and cost, not just what's familiar.

How to answer

  • A single simple part usually goes faster on a manual machine than writing and proving a program
  • Complex shapes, curves, or anything needing repeat accuracy go to the CNC
  • Consider which machine is free and what else is waiting
  • Give a real example of a job you moved from one to the other

Part 2

6.Read this callout on the print and tell me what it means.

Why they ask

Print reading is the core of the job, and GD&T symbols trip up a lot of candidates. They usually point at a position, flatness, or runout callout.

How to answer

  • Name the symbol and what it controls
  • Identify the datums it refers to and which surface you'd locate from
  • Explain how you'd check it with the tools in their shop
  • Say plainly if a symbol is new to you and how you'd look it up
7.What do you leave for heat treat or grinding, and why?

Why they ask

Parts that go out for hardening come back changed. Knowing to plan for that shows you think past your own machine.

How to answer

  • Leave grind stock on surfaces that need to finish hard and to size
  • Expect some distortion and scale after heat treat
  • Finish non-critical features before hardening, since they're harder to cut after
  • Follow the print or ask the engineer when the stock amount isn't called out
8.You break a tap deep in a customer's part. What now?

Why they ask

Everyone breaks a tap. They want to know if you panic, hide it, or fix it properly.

How to answer

  • Stop and tell the lead, especially if it's a customer's expensive part
  • Try a tap extractor if the flutes are exposed
  • Mention EDM tap burning or careful drilling out as options
  • Explain what caused it, like a dull tap, the wrong drill size, or no lube, and how you'd prevent it
9.Tell me about a part you scrapped. What happened?

Why they ask

Every machinist has scrapped work. Someone who says they never have is either new or not being straight.

How to answer

  • Pick a real part and say what went wrong in plain terms
  • Say when you caught it and who you told
  • Explain what you changed in your routine afterward
10.What tools do you bring, and how do you look after them?

Why they ask

Many shops expect you to have your own hand tools and precision instruments. How you care for them says a lot about how you'll care for their machines.

How to answer

  • List what's in your box: micrometers, calipers, indicators, edge finder, hand tools
  • Explain how you check them against standards and keep them clean
  • Mention what you'd expect the shop to supply, like gauge blocks or height gauges

Part 3

11.How do you handle a rush job when you're already mid-setup on something else?

Why they ask

Job shops get interrupted constantly. They want to see that you can switch without losing track or losing quality.

How to answer

  • Check with the foreman on which job wins
  • Note exactly where you stopped on the first job, including offsets and which cuts are done
  • Leave the setup in a state someone else could understand
  • Go back and recheck the first part before cutting again
12.Why do you want to work in this shop?

Why they ask

They want to know you'll stay after they've spent time training you on their machines and customers.

How to answer

  • Mention something specific you saw on the walk or read about their work
  • Connect it to the kind of machining you want more of
  • Keep it short and honest

Questions to ask them

Ask at least two. It shows you're picking them too.

  • What's the split between manual and CNC work here, and which machines would I start on?
  • Who programs the CNC jobs, and do machinists edit at the control?
  • How do you handle first-article inspection on one-off parts?
  • What kind of repair or rush work comes in, and how often does it bump the schedule?
  • Do you help pay for tools or classes if I want to add skills like grinding or CAM?

Related interview guides

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