It is a reasonable thing to wonder before an interview, and the honest answer is that many shops do test your G-code knowledge, just rarely in the way people fear. There is usually no hard written exam. It is a short, practical check that you can read a program before they trust you with one.
How shops usually test it
- A short quiz. A handful of code questions, on paper or verbally.
- A program to read. They hand you a printout and ask what it does, block by block.
- Questions at the machine. Pointing at a line and asking you to explain it.
The depth scales with the role: an operator role checks the common codes; a setter or programmer role goes into offsets, compensation, and cycles.
| Role | Likely depth |
|---|---|
| Operator | Read common codes, explain a block |
| Setter | Offsets, tooling, full-program reading |
| Programmer | Compensation, cycles, writing code |
How to make it a non-event
Whatever form it takes, the test rewards fluent reading, which is recall you can build in advance. Drill the common G-codes and common M-codes with beginner CNC code practice, and for worked examples see CNC practical test examples for a job interview and how to read a G-code print for an interview test. A free tool like G-Code Sprint makes the reading automatic.
Bottom line
Yes, many shops test your G-code knowledge, usually with a short quiz, a program to read, or questions at the machine, scaled to the role. Build fluent recall of the common codes and that test becomes the easy part of the interview.
Sources
- NIMS (National Institute for Metalworking Skills)
- LinuxCNC G-code reference
- CNCCookbook: G-code and M-code cheat sheet
Frequently asked questions
Do machine shops test G-code knowledge when hiring?
Many do, though usually informally: a short quiz, a program to read and explain, or questions at the machine. They are confirming you can read a program safely, not giving a hard written exam. The level depends on the role.
What kind of G-code test does a shop give?
Commonly reading a short program and saying what it does, identifying common codes, and the standard comparisons like G00 vs G01. For setter or programmer roles it goes deeper into offsets and cycles.
How do I pass a shop’s G-code test?
Make reading automatic by drilling the common codes for recall. A free tool like G-Code Sprint builds that fluency, so whatever form the shop’s test takes, the code questions are the easy part.
G-Code Sprint is a study and practice tool only. Always follow your instructor, employer, machine manual, and shop safety procedures.