CNC Study Guide 2026
Everything you need to pass the CNC exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CNC Exam Format at a Glance
📚 CNC Topics to Study (69)
✍️ Sample CNC Questions & Answers
1. What is the function of M30 in a CNC program?
M30 ends the program, rewinds to the beginning, and resets all modal states, readying the machine for the next run.
2. What is spindle speed measured in?
Spindle speed, which dictates how fast the cutting tool or workpiece rotates, is universally measured in Revolutions Per Minute (RPM). This measurement is a critical parameter in CNC machining, directly influencing the cutting speed, material removal rate, and surface finish. Proper RPM selection is essential for optimizing tool life and machining efficiency for different materials.
3. Which stainless steel family is generally non-magnetic and cannot be hardened by heat treatment?
Austenitic stainless steels (300 series) retain their FCC crystal structure at room temperature, making them non-magnetic and hardenable only by cold working.
4. On a feature control frame reading ⌀0.005 M A B, what does the symbol M indicate?
The MMC modifier (M) means bonus tolerance equal to the departure from MMC is added to the stated tolerance as the feature's actual size moves away from MMC.
5. In CNC programming, what does the G28 command instruct the machine to do?
G28 commands the machine to return to its machine home (reference zero) position, typically passing through an intermediate point for safety.
6. When a drawing calls for a 'ground' surface, which post-processing step is implied?
A 'ground' callout means the surface is finished by grinding, achieving tolerances and finishes beyond what turning or milling alone can produce.