South Carolina CNC Machinist
Certification License Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. What is the primary purpose of using G-code in CNC machining?
A. To monitor machine temperature
B. To control tool movement and machine functions
C. To design parts in CAD software
D. To lubricate the cutting tools
The rationale: G-code is the standard programming language used in
CNC machining to dictate tool paths, axis movements, and auxiliary
functions necessary to produce the desired part._
2. Which axis on a 3-axis CNC mill represents vertical movement?
A. X-axis
B. Y-axis
C. Z-axis
D. A-axis
The rationale: The Z-axis in CNC milling refers to vertical movement,
allowing the tool to move up and down relative to the workpiece._
3. In CNC terminology, what does “RPM” stand for?
A. Rapid Path Motion
, B. Revolutions Per Minute
C. Rate Per Module
D. Radial Precision Measure
The rationale: RPM measures the number of rotations the spindle
makes each minute, which is critical for determining cutting speeds
and surface finish._
4. Which of the following materials is considered ferrous?
A. Aluminum
B. Steel
C. Brass
D. Plastic
The rationale: Ferrous materials contain iron, and steel is a common
ferrous metal widely machined in CNC operations._
5. What is the purpose of a tool offset in CNC machining?
A. To change coolant type
B. To store part drawings
C. To correct tool length and diameter variations
D. To adjust machine temperature
The rationale: Tool offsets compensate for differences in actual tool
length and diameter, ensuring accurate positioning and cuts during
machining._
6. Which coolant type is most commonly used for general milling
operations?
A. Dry ice
B. Water-soluble cutting fluid
C. Compressed air
D. Vegetable oil
The rationale: Water-soluble cutting fluids provide effective cooling
, and lubrication for a wide range of milling processes, making them
standard in many shops._
7. What does “feed rate” control in CNC machining?
A. Spindle bearing temperature
B. Tool wear compensation
C. Speed at which the tool advances through material
D. Coolant concentration
The rationale: Feed rate defines how quickly the cutting tool
advances relative to the workpiece, which directly affects surface
finish and tool life._
8. In CNC programming, what symbol typically precedes a line number?
A. %
B. *
C. N
D. T
The rationale: N is used to designate line numbers in a CNC program
for easier reference and editing._
9. Which safety device should always be used when operating a CNC
lathe?
A. Earbuds
B. Machine guarding/shields
C. Open-toed shoes
D. Loose gloves
The rationale: Proper machine guarding prevents contact with
rotating components and flying chips, which is essential for safe lathe
operation._
10. What is the typical unit for specifying spindle speed in CNC
programming?
A. Inches per minute
Certification License Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. What is the primary purpose of using G-code in CNC machining?
A. To monitor machine temperature
B. To control tool movement and machine functions
C. To design parts in CAD software
D. To lubricate the cutting tools
The rationale: G-code is the standard programming language used in
CNC machining to dictate tool paths, axis movements, and auxiliary
functions necessary to produce the desired part._
2. Which axis on a 3-axis CNC mill represents vertical movement?
A. X-axis
B. Y-axis
C. Z-axis
D. A-axis
The rationale: The Z-axis in CNC milling refers to vertical movement,
allowing the tool to move up and down relative to the workpiece._
3. In CNC terminology, what does “RPM” stand for?
A. Rapid Path Motion
, B. Revolutions Per Minute
C. Rate Per Module
D. Radial Precision Measure
The rationale: RPM measures the number of rotations the spindle
makes each minute, which is critical for determining cutting speeds
and surface finish._
4. Which of the following materials is considered ferrous?
A. Aluminum
B. Steel
C. Brass
D. Plastic
The rationale: Ferrous materials contain iron, and steel is a common
ferrous metal widely machined in CNC operations._
5. What is the purpose of a tool offset in CNC machining?
A. To change coolant type
B. To store part drawings
C. To correct tool length and diameter variations
D. To adjust machine temperature
The rationale: Tool offsets compensate for differences in actual tool
length and diameter, ensuring accurate positioning and cuts during
machining._
6. Which coolant type is most commonly used for general milling
operations?
A. Dry ice
B. Water-soluble cutting fluid
C. Compressed air
D. Vegetable oil
The rationale: Water-soluble cutting fluids provide effective cooling
, and lubrication for a wide range of milling processes, making them
standard in many shops._
7. What does “feed rate” control in CNC machining?
A. Spindle bearing temperature
B. Tool wear compensation
C. Speed at which the tool advances through material
D. Coolant concentration
The rationale: Feed rate defines how quickly the cutting tool
advances relative to the workpiece, which directly affects surface
finish and tool life._
8. In CNC programming, what symbol typically precedes a line number?
A. %
B. *
C. N
D. T
The rationale: N is used to designate line numbers in a CNC program
for easier reference and editing._
9. Which safety device should always be used when operating a CNC
lathe?
A. Earbuds
B. Machine guarding/shields
C. Open-toed shoes
D. Loose gloves
The rationale: Proper machine guarding prevents contact with
rotating components and flying chips, which is essential for safe lathe
operation._
10. What is the typical unit for specifying spindle speed in CNC
programming?
A. Inches per minute
