Lists of topics are easy to nod along to and hard to actually use. Worked examples are better, because they show you the exact shape of the questions. Here are realistic ones with the answers.

Sample questions and answers

  • “What does G01 X50 F150 do?” A straight-line feed move to X50 at a feedrate of 150 units per minute. It is a cutting move.
  • “What is the difference between G00 and G01?” G00 is a rapid (fast, non-cutting positioning); G01 is a controlled feed move that cuts. See G00 vs G01.
  • “What does M03 do, and M05?” M03 starts the spindle clockwise; M05 stops it.
  • “G02 or G03 for a counterclockwise arc?” G03. G02 is clockwise. See G02 vs G03.
  • “How do you know if a program is in inches or millimeters?” Look for G20 (inch) or G21 (millimeters).
  • “What does G90 mean?” Absolute positioning: coordinates are measured from part zero.

Quick-reference answers

QuestionAnswer
G00 vs G01Rapid (no cut) vs linear feed (cut)
M03 / M05Spindle on clockwise / spindle stop
Counterclockwise arcG03 (G02 is clockwise)
Inch vs metricG20 (inch) / G21 (mm)
G90Absolute positioning from part zero
G91Incremental positioning from current point

How to practice

Every answer above is recall of a common code, so the prep is recall practice, not re-reading. Drill the common G-codes and common M-codes both directions, put extra reps on the mix-ups, and rehearse under a timer so the answers come fast. That is the method in beginner CNC code practice, and the timed mode in G-Code Sprint mirrors the pressure of being asked out loud. For the broader interview, see the G-code test for a job interview.

Bottom line

CNC practical tests mix short program reading with direct code recall. Practice the exact question types as recall drills, with a timer, and the interview becomes a review rather than a surprise.

Sources

Frequently asked questions

What kind of questions are on a CNC practical test?

A mix of reading a short program, identifying what individual codes do, and the common comparisons like G00 vs G01 or G02 vs G03. Some also include basic measurement and safety questions.

Do CNC interviews ask you to write G-code?

Entry-level interviews usually ask you to read and explain code more than write it from scratch. They want to see you understand what a program does and can spot the common codes confidently.

What is the best way to practice CNC interview questions?

Turn the question types into recall drills. A free tool like G-Code Sprint quizzes code-to-meaning, meaning-to-code, and the common mix-ups, with a timed mode that mirrors interview pressure.

G-Code Sprint is a study and practice tool only. Always follow your instructor, employer, machine manual, and shop safety procedures.