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CNC Machine Maintenance Technician
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
___________________________________________________________________
1. What is the primary purpose of preventive maintenance on a CNC machine?
A. Increase programming speed
B. Eliminate the need for operators
C. Reduce unexpected downtime and maintain machine accuracy
D. Increase spindle speed permanently
Answer: C. Reduce unexpected downtime and maintain machine accuracy
Rationale: Preventive maintenance identifies and corrects wear, contamination,
lubrication problems, and other developing faults before they cause failures or
loss of accuracy.
2. Which component converts electrical energy into mechanical rotational
motion in a CNC machine?
A. Proximity switch
B. Encoder
C. Servo motor
D. PLC input
Answer: C. Servo motor
Rationale: A servo motor converts electrical commands from the drive system
into controlled mechanical motion for an axis or spindle.
,3. What is the main function of way lubrication?
A. Cool the cutting tool
B. Increase hydraulic pressure
C. Reduce friction and wear between sliding machine surfaces
D. Increase spindle RPM
Answer: C. Reduce friction and wear between sliding machine surfaces
Rationale: Proper way lubrication creates a protective film that minimizes
friction, wear, and heat between machine guide surfaces.
4. What should be done before performing electrical maintenance inside a CNC
control cabinet?
A. Increase the spindle speed
B. Remove the machine coolant
C. Apply proper lockout/tagout and verify absence of hazardous energy
D. Reset the CNC control
Answer: C. Apply proper lockout/tagout and verify absence of hazardous energy
Rationale: Lockout/tagout prevents unexpected energization, while verification
confirms that hazardous electrical and mechanical energy has been isolated.
5. Which device commonly provides position feedback to a CNC servo system?
A. Solenoid valve
B. Pressure switch
C. Encoder
D. Fuse
Answer: C. Encoder
Rationale: An encoder provides position and, depending on the system, velocity
information to the CNC control for closed-loop motion control.
6. What is a common symptom of insufficient spindle lubrication?
,A. Lower coolant concentration
B. Excessive spindle temperature or abnormal noise
C. Increased air pressure
D. Improved surface finish
Answer: B. Excessive spindle temperature or abnormal noise
Rationale: Insufficient lubrication can increase bearing friction, resulting in heat
generation, noise, vibration, and eventual spindle damage.
7. What is the purpose of a CNC machine's hydraulic system?
A. Program the machine
B. Provide controlled hydraulic power for functions such as clamping or tool
operation
C. Generate electrical signals
D. Measure tool diameter
Answer: B. Provide controlled hydraulic power for functions such as clamping or
tool operation
Rationale: Hydraulic systems provide high-force actuation for applications such
as workholding, clamping, braking, and certain tool-changing mechanisms.
8. What is the most likely effect of contaminated hydraulic oil?
A. Improved valve operation
B. Increased electrical conductivity
C. Valve sticking, component wear, and unreliable operation
D. Lower mechanical wear
Answer: C. Valve sticking, component wear, and unreliable operation
Rationale: Dirt and other contaminants can damage precision hydraulic
components and interfere with valve movement and pressure control.
9. What does a machine's emergency-stop circuit primarily do?
, A. Save the CNC program
B. Increase axis acceleration
C. Bring hazardous machine functions to a safe stopped condition
D. Improve cutting accuracy
Answer: C. Bring hazardous machine functions to a safe stopped condition
Rationale: An emergency stop is designed to rapidly stop hazardous machine
operations when an immediate safety intervention is necessary.
10. Which instrument is commonly used to measure electrical voltage?
A. Micrometer
B. Pressure gauge
C. Digital multimeter
D. Dial indicator
Answer: C. Digital multimeter
Rationale: A digital multimeter can measure voltage and, depending on its
configuration, resistance, current, continuity, and other electrical parameters.
11. What does excessive backlash in a CNC axis commonly cause?
A. Higher coolant pressure
B. Positioning errors and poor contour accuracy
C. Higher electrical insulation
D. Improved repeatability
Answer: B. Positioning errors and poor contour accuracy
Rationale: Backlash is unwanted mechanical clearance that can cause lost
motion when an axis reverses direction.
12. Which component is commonly responsible for converting rotary motor
motion into linear axis movement?
CNC Machine Maintenance Technician
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A Instant Download Pdf
___________________________________________________________________
1. What is the primary purpose of preventive maintenance on a CNC machine?
A. Increase programming speed
B. Eliminate the need for operators
C. Reduce unexpected downtime and maintain machine accuracy
D. Increase spindle speed permanently
Answer: C. Reduce unexpected downtime and maintain machine accuracy
Rationale: Preventive maintenance identifies and corrects wear, contamination,
lubrication problems, and other developing faults before they cause failures or
loss of accuracy.
2. Which component converts electrical energy into mechanical rotational
motion in a CNC machine?
A. Proximity switch
B. Encoder
C. Servo motor
D. PLC input
Answer: C. Servo motor
Rationale: A servo motor converts electrical commands from the drive system
into controlled mechanical motion for an axis or spindle.
,3. What is the main function of way lubrication?
A. Cool the cutting tool
B. Increase hydraulic pressure
C. Reduce friction and wear between sliding machine surfaces
D. Increase spindle RPM
Answer: C. Reduce friction and wear between sliding machine surfaces
Rationale: Proper way lubrication creates a protective film that minimizes
friction, wear, and heat between machine guide surfaces.
4. What should be done before performing electrical maintenance inside a CNC
control cabinet?
A. Increase the spindle speed
B. Remove the machine coolant
C. Apply proper lockout/tagout and verify absence of hazardous energy
D. Reset the CNC control
Answer: C. Apply proper lockout/tagout and verify absence of hazardous energy
Rationale: Lockout/tagout prevents unexpected energization, while verification
confirms that hazardous electrical and mechanical energy has been isolated.
5. Which device commonly provides position feedback to a CNC servo system?
A. Solenoid valve
B. Pressure switch
C. Encoder
D. Fuse
Answer: C. Encoder
Rationale: An encoder provides position and, depending on the system, velocity
information to the CNC control for closed-loop motion control.
6. What is a common symptom of insufficient spindle lubrication?
,A. Lower coolant concentration
B. Excessive spindle temperature or abnormal noise
C. Increased air pressure
D. Improved surface finish
Answer: B. Excessive spindle temperature or abnormal noise
Rationale: Insufficient lubrication can increase bearing friction, resulting in heat
generation, noise, vibration, and eventual spindle damage.
7. What is the purpose of a CNC machine's hydraulic system?
A. Program the machine
B. Provide controlled hydraulic power for functions such as clamping or tool
operation
C. Generate electrical signals
D. Measure tool diameter
Answer: B. Provide controlled hydraulic power for functions such as clamping or
tool operation
Rationale: Hydraulic systems provide high-force actuation for applications such
as workholding, clamping, braking, and certain tool-changing mechanisms.
8. What is the most likely effect of contaminated hydraulic oil?
A. Improved valve operation
B. Increased electrical conductivity
C. Valve sticking, component wear, and unreliable operation
D. Lower mechanical wear
Answer: C. Valve sticking, component wear, and unreliable operation
Rationale: Dirt and other contaminants can damage precision hydraulic
components and interfere with valve movement and pressure control.
9. What does a machine's emergency-stop circuit primarily do?
, A. Save the CNC program
B. Increase axis acceleration
C. Bring hazardous machine functions to a safe stopped condition
D. Improve cutting accuracy
Answer: C. Bring hazardous machine functions to a safe stopped condition
Rationale: An emergency stop is designed to rapidly stop hazardous machine
operations when an immediate safety intervention is necessary.
10. Which instrument is commonly used to measure electrical voltage?
A. Micrometer
B. Pressure gauge
C. Digital multimeter
D. Dial indicator
Answer: C. Digital multimeter
Rationale: A digital multimeter can measure voltage and, depending on its
configuration, resistance, current, continuity, and other electrical parameters.
11. What does excessive backlash in a CNC axis commonly cause?
A. Higher coolant pressure
B. Positioning errors and poor contour accuracy
C. Higher electrical insulation
D. Improved repeatability
Answer: B. Positioning errors and poor contour accuracy
Rationale: Backlash is unwanted mechanical clearance that can cause lost
motion when an axis reverses direction.
12. Which component is commonly responsible for converting rotary motor
motion into linear axis movement?
