CNC MACHINIST CERTIFICATION EXAM
PRACTICE QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF
1. What does CNC stand for?
A. Computerized Numeric Conversion
B. Computer Numerical Control
C. Controlled Numeric Computation
D. Computed Number Control
Rationale: CNC means Computer Numerical Control, referring to
automated machine tool operation via programmed commands.
2. What is the main function of G-code in CNC programming?
A. It provides motion and control commands to the machine tool.
B. It sets tool offsets only.
C. It adjusts the feed rate automatically.
D. It manages coolant flow only.
Rationale: G-codes tell the machine how to move — defining paths,
speeds, and motions.
3. What does M-code control in CNC machines?
A. Tool path movement
,B. Coordinate positioning
C. Machine auxiliary functions
D. Material feed
Rationale: M-codes handle auxiliary functions like spindle start/stop and
coolant.
4. What does the G00 command do?
A. Rapid positioning move
B. Linear interpolation
C. Circular interpolation
D. Tool change
Rationale: G00 moves the tool quickly to a new location without cutting.
5. Which coordinate system is most common in CNC machining?
A. Polar
B. Cartesian (X, Y, Z)
C. Cylindrical
D. Spherical
Rationale: Most CNC machines use a Cartesian coordinate system.
6. In G-code, what does G01 command indicate?
A. Linear interpolation (cutting move)
B. Rapid move
C. Circular clockwise motion
D. Tool change
Rationale: G01 specifies a cutting motion along a straight line.
, 7. What is the purpose of a tool offset?
A. To speed up the cutting feed rate
B. To compensate for tool length and diameter differences
C. To reduce vibration
D. To increase spindle speed
Rationale: Offsets adjust for each tool’s unique dimensions.
8. What is the spindle speed measured in?
A. Inches per minute
B. Revolutions per minute (RPM)
C. Feet per minute
D. Millimeters per second
Rationale: Spindle speed represents rotations per minute.
9. What does feed rate control?
A. Spindle speed
B. Cutting tool movement speed through material
C. Coolant flow
D. Tool sharpness
Rationale: Feed rate determines how quickly the tool advances through
the material.
10. What is backlash in a CNC machine?
A. Tool vibration
B. Lost motion due to clearance or wear between mechanical parts
C. Incorrect feed rate
D. Overheating of spindle bearings
PRACTICE QUESTIONS AND CORRECT
ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF
1. What does CNC stand for?
A. Computerized Numeric Conversion
B. Computer Numerical Control
C. Controlled Numeric Computation
D. Computed Number Control
Rationale: CNC means Computer Numerical Control, referring to
automated machine tool operation via programmed commands.
2. What is the main function of G-code in CNC programming?
A. It provides motion and control commands to the machine tool.
B. It sets tool offsets only.
C. It adjusts the feed rate automatically.
D. It manages coolant flow only.
Rationale: G-codes tell the machine how to move — defining paths,
speeds, and motions.
3. What does M-code control in CNC machines?
A. Tool path movement
,B. Coordinate positioning
C. Machine auxiliary functions
D. Material feed
Rationale: M-codes handle auxiliary functions like spindle start/stop and
coolant.
4. What does the G00 command do?
A. Rapid positioning move
B. Linear interpolation
C. Circular interpolation
D. Tool change
Rationale: G00 moves the tool quickly to a new location without cutting.
5. Which coordinate system is most common in CNC machining?
A. Polar
B. Cartesian (X, Y, Z)
C. Cylindrical
D. Spherical
Rationale: Most CNC machines use a Cartesian coordinate system.
6. In G-code, what does G01 command indicate?
A. Linear interpolation (cutting move)
B. Rapid move
C. Circular clockwise motion
D. Tool change
Rationale: G01 specifies a cutting motion along a straight line.
, 7. What is the purpose of a tool offset?
A. To speed up the cutting feed rate
B. To compensate for tool length and diameter differences
C. To reduce vibration
D. To increase spindle speed
Rationale: Offsets adjust for each tool’s unique dimensions.
8. What is the spindle speed measured in?
A. Inches per minute
B. Revolutions per minute (RPM)
C. Feet per minute
D. Millimeters per second
Rationale: Spindle speed represents rotations per minute.
9. What does feed rate control?
A. Spindle speed
B. Cutting tool movement speed through material
C. Coolant flow
D. Tool sharpness
Rationale: Feed rate determines how quickly the tool advances through
the material.
10. What is backlash in a CNC machine?
A. Tool vibration
B. Lost motion due to clearance or wear between mechanical parts
C. Incorrect feed rate
D. Overheating of spindle bearings
