This is one of the most common worries before a NIMS test, and the answer is reassuring: no, you do not need to memorize the entire G-code standard. There are dozens of codes, and many appear rarely. What you do need is fast recall of the common ones, because a timed test does not give you time to look up every line.
Memorize, understand, or reference
The codes fall into three buckets, and treating them all the same is the mistake:
- Memorize (instant recall): the common core that appears in almost every program. You should answer these without thinking.
- Understand (concept-level): how compensation, work offsets, and canned cycles work, even if you would check exact parameters.
- Reference (look up): the rare codes and machine-specific options you simply recognize and look up when needed.
Where the line sits
| Bucket | Examples | What is expected |
|---|---|---|
| Memorize | G00-G03, M03/M05, G20/G21, G90/G91 | Instant, two-way recall |
| Understand | G43, G54-G59, canned cycles like G81 | Explain what they do |
| Reference | Rare codes, machine options | Recognize and look up |
The common core is small, maybe fifteen to twenty codes, which is exactly why it is realistic to know them cold. The full common G-codes list and common M-codes list cover the memorize bucket.
How to memorize the core
Re-reading a chart builds recognition, not recall, so it falls apart on a timed test. Drill retrieval instead, the method in how to memorize G-code faster and beginner CNC code practice. For what the test covers overall, see CNC machinist certification test prep and the NIMS CNC operator test guide. A free tool like G-Code Sprint drills the core for fast recall.
Bottom line
You do not memorize every G-code for the NIMS test. You memorize the common core for instant recall, understand the key concepts, and look up the rest. Confirm your test’s format, then drill the core until it is automatic.
Sources
- NIMS (National Institute for Metalworking Skills)
- LinuxCNC G-code reference
- CNCCookbook: G-code and M-code cheat sheet
Frequently asked questions
Do you have to memorize all G-codes for the NIMS test?
No. You need fluent recall of the common codes that appear in almost every program, plus an understanding of the concepts. The rarer codes you only need to recognize and be able to look up, not memorize cold.
Is the NIMS knowledge test closed-book?
Formats vary, so confirm with your testing site. Either way, a timed test rewards recall, because looking up every code is too slow. Treat the common codes as something you know instantly.
What is the best way to memorize the codes I do need?
Active recall, not re-reading. A free tool like G-Code Sprint drills the common G-code and M-code both directions and repeats the ones you miss, which is how you build the fast recall a timed test needs.
G-Code Sprint is a study and practice tool only. It is not affiliated with NIMS and does not provide official exam content. Always follow your instructor, employer, machine manual, and shop safety procedures.