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Quizzes > Programming & Software

CNC Test: Check Your G-Code Programming Skills

Quick, free G-code programming quiz. Instant results.

Editorial: Review CompletedCreated By: Sebastian QuerelosUpdated Aug 26, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art coral background with stylized CNC turret G code and quiz on programming turret numbering coolant use

This CNC test helps you practice core G-code tasks like turret numbering, absolute moves, and coolant codes. Get instant results to spot gaps before an exam or a skills check; for more practice, try our cnc machinist test and build measurement skills with a caliper reading quiz.

What G-code is used for rapid positioning?
G3
G0
G2
G1
G0 is the G-code for rapid positioning, which moves the tool at maximum speed to a specified location without cutting. Rapid moves optimize cycle time by quickly repositioning the tool. Programmers switch to G1 for controlled cutting feeds.
Which G-code indicates linear interpolation (controlled tool movement)?
G1
G2
G0
G3
G1 is used for linear interpolation, where the tool moves at a specified feed rate in a straight line. It is fundamental for precise cutting operations. Without G1, the machine would not regulate the tool feed during material removal.
What G-code switches the control to absolute coordinate programming mode?
G94
G90
G92
G91
G90 sets the CNC machine to absolute coordinate mode, meaning all coordinate positions are measured from a fixed zero point. Absolute programming ensures consistency in part geometry. In contrast, G91 enables incremental mode, where positions are relative to the current location.
Which G-code sets the control to incremental (relative) coordinate mode?
G91
G90
G92
G28
G91 activates incremental mode where movements are specified relative to the tool's current position. This mode is useful for repetitive patterns or successive cuts. Users must switch back to G90 to resume absolute positioning.
What M-code turns the flood coolant on?
M6
M7
M9
M8
M8 activates flood coolant in most CNC controls, providing ample coolant flow for machining operations. This helps maintain tool life and part finish. M7 typically turns on mist coolant, while M9 shuts off all coolant.
What M-code turns all coolant off?
M9
M7
M6
M8
M9 deactivates all coolant in the machine, stopping both mist and flood systems. This is often used at the end of a cut or before a tool change. Proper coolant management prevents leaks and machine damage.
In CNC turret numbering on a lathe, what does T01 typically refer to?
Spindle speed setting
First turret station
Axis assignment
Tool offset register 1
T01 ordinarily designates the first turret station on a CNC lathe, indicating where the first tool is mounted. Correct turret numbering is essential for accurate tool changes. Programmers match tool numbers in the code to turret positions.
What does the G54 code represent in CNC programming?
First work coordinate offset
Spindle speed unit
Machine home return
Tool length compensation
G54 sets the first work coordinate system origin, defining where part zero is located on the machine table. This allows multiple setups or fixtures. Additional offsets G55 - G59 provide other work origins.
What is the standard file extension commonly used for CNC G-code program files?
.cn
.gcode
.tap
.nc
The .nc extension is widely used for CNC G-code program files, standing for 'numerical control.' Many CAM systems output NC files for direct use on CNC machines. Other extensions exist, but .nc is the most common.
Which G-code introduces a programmed dwell (pause) for a specified time?
G04
G00
G09
G03
G04 is the dwell code, pausing machine motion for a set duration specified in seconds or milliseconds. It's often used for tapping or allowing coolant to clear chips. Other G-codes control motion rather than time delay.
How do you specify a clockwise circular interpolation in G-code?
G03
G02
G00
G01
G02 instructs the machine to move the tool in a clockwise arc. It requires end point coordinates and either center offsets (I, J) or radius. G03 is used for counterclockwise movements.
In arc programming, what do the I and J parameters represent?
Feed rate adjustments
X and Y offsets to the arc center from the start point
End point coordinates
Polar angles
I and J define the vector from the arc's start point to its center along X and Y axes. They are essential for specifying the circle's geometry. Without correct I and J values, the arc will be mis-centered.
What is the purpose of tool length offset (G43) in CNC machining?
To recalibrate work zero
To adjust spindle speed
To change feed direction
To compensate for variation in tool length
G43 applies positive tool length compensation using the offset value stored in the tool length register. It ensures the programmed Z-height accounts for each tool's actual length. This prevents crashes and maintains part accuracy.
Which M-code is used to call a subprogram in Fanuc-style G-code?
M98
M96
M97
M99
M98 calls a subprogram (typically stored separately with an O-number) and then returns control to the main program after completion. M99 ends or loops within subroutines. Subprograms help modularize CNC code for repeated tasks.
Which G-code applies positive tool length compensation?
G49
G43
G42
G41
G43 invokes positive tool length compensation based on the value in the selected tool length offset register. G42/G41 are cutter diameter compensation, and G49 cancels length compensation. Correct use avoids under- or over-cutting.
What M-code initiates a tool change sequence?
M01
M06
M05
M03
M06 triggers the automatic tool change, bringing the turret or tool changer to swap the current tool with the specified one. It's one of the most commonly used M-codes in CNC programs. M05 stops the spindle, M03 starts it clockwise.
Which G-code returns the machine to its reference (home) position?
G30
G28
G92
G54
G28 moves the machine to the predefined machine home position via an intermediate point. It's commonly used at the end of a program for safety and repeatability. G30 can also return to a second home position if defined.
Which G-code cancels cutter diameter compensation?
G40
G43
G42
G41
G40 switches off cutter diameter compensation, returning the tool path to the programmed centerline. This must be done before any non-compensated moves. G41 and G42 apply left and right compensation respectively.
In a G1 command, what does the F-word specify?
Tool number
Spindle speed
Coolant type
Feed rate
The F-word in G1 specifies the feed rate at which the tool moves during cutting. It's typically measured in units per minute (inches or millimeters per minute). Proper feed selection is critical for surface finish and tool life.
Which M-code sets the spindle to rotate counterclockwise?
M05
M03
M08
M04
M04 commands the spindle to run counterclockwise, commonly used for reverse milling or back-spotfacing. M03 is used for clockwise rotation, and M05 stops the spindle. Coolant codes are separate M-codes.
How would you program helical interpolation for a threaded feature using G-code?
Apply G17 for helical mode
Use G47 threading code
Call G84 canned cycle
Use G02/G03 with simultaneous Z-axis increment
Helical interpolation is achieved by combining an arc move (G02 or G03) with a linear Z-axis feed, creating a spiral path. This method is often used for threading or deep hole milling. It requires coordinated axis motion and correct radius or center offsets.
What is the function of G64 in CNC machining?
Set spindle speed limit
Feed rate override lock
Exact stop at each block
Continuous mode with path blending
G64 enables continuous mode, allowing the controller to blend tool paths between blocks for smoother motion and higher speeds. This improves cycle time by reducing dwell at each block. G61 is used for exact stops instead.
Which macro variable prefix is used for system and special functions on Fanuc controls?
@
$
##
#
System and special function macro variables on Fanuc controls use the double-hash prefix (##), while local variables use single-hash (#). These variables provide machine data and system status for advanced logic. Proper prefix usage prevents variable conflicts.
What is the effect of applying G68 in a CNC program?
Mirror-image compensation
Linear axis backlash compensation
Scaling of axes
Coordinate rotation
G68 performs a coordinate system rotation about the machine origin by a specified angle. This allows machining features at rotated orientations without reprogramming raw coordinates. G69 cancels the rotation.
Which G-code commands compensation to the right of the programmed path?
G42
G41
G40
G43
G42 applies cutter diameter compensation to the right side of the programmed toolpath, shifting the tool to maintain the programmed contour. G41 is used for left-side compensation, and G40 cancels compensation.
In G02/G03 arc programming, what does the K parameter specify?
Z-axis offset to the arc center
Feed rate
X-axis end point
Radius of the arc
K defines the distance along the Z-axis from the start point to the center of the arc in 3-axis arc motions. I and J cover X and Y offsets respectively. Correct K values are essential for helical or tilted arcs.
Which M-code performs an optional stop, allowing the operator to resume manually?
M00
M30
M99
M01
M01 is the optional stop code that pauses program execution if the optional stop switch is enabled, letting the operator inspect or adjust before continuing. M00 is an unconditional stop. M30 ends and rewinds the program.
Which G-code resets the spindle speed limit to its preset maximum?
G52
G50
G49
G53
G50 sets the spindle speed limit to the maximum value defined in the control for safety or setup purposes. It's commonly used before a high-speed section to prevent overspeed. G52 and G53 are coordinate system commands, and G49 cancels tool length compensation.
What cycle does the G83 canned cycle perform?
Peck drilling
Deep tapping
Counterboring
Boring
G83 is the peck drilling cycle that retracts the drill to clear chips at set intervals, preventing chip packing in deep holes. It's vital for deep-hole accuracy and tool life. Other cycles like G85 perform boring or shallow drilling.
Which G-code activates polar coordinate programming?
G15
G16
G17
G18
G16 enables polar coordinate programming, allowing positions to be specified by radius and angle rather than Cartesian X and Y. This is useful for circular patterns. G17, G18, and G19 select planes for arc moves.
In a macro call using M98, what does the L parameter specify?
Line number entry
Local variable index
Subprogram number
Number of repetitions
In Fanuc macro calls, the L parameter following M98 indicates how many times to repeat the specified subprogram. This facilitates loops and repeated operations without rewriting code. P specifies the subprogram number.
Which G-code selects the YZ plane for arc and canned cycle operations?
G18
G19
G20
G17
G19 selects the YZ plane for circular interpolation and canned cycles like drilling. G17 selects XY plane and G18 selects XZ plane for arcs. Choosing the correct plane ensures proper tool movement.
Which M-code ends the program and rewinds it to the start in most CNC controls?
M00
M30
M99
M02
M30 ends the program and resets it to the beginning, readying the control for the next cycle. M02 also ends the program but does not rewind to the start. M00 is a program stop, and M99 returns from subprograms.
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Study Outcomes

  1. Identify Turret Numbering Schemes -

    Distinguish turret station numbers in our turret numbering quiz and apply correct tool offsets for precise part setup.

  2. Apply Absolute Programming Principles -

    Interpret absolute programming questions in G-code to ensure accurate coordinate positioning and consistent machining results.

  3. Optimize Coolant Usage -

    Select appropriate coolant types and adjust flow rates to enhance tool life and achieve superior surface finishes on your parts.

  4. Interpret G-Code Syntax -

    Analyze common G-code commands featured in a CNC programming quiz and troubleshoot basic coding errors effectively.

  5. Evaluate CNC Programming Strategies -

    Compare different approaches in a CNC machine programming test to improve cycle times and operational efficiency.

  6. Assess Your Skills with a CNC Machining Quiz -

    Engage with our free CNC test quiz to pinpoint strengths, identify learning gaps, and drive continuous improvement.

Cheat Sheet

  1. Turret Numbering Conventions -

    Understand the ISO 6983 standard for turret numbering to quickly recall tool positions: T1 for the first tool pocket, T2 for the second, and so on. A simple mnemonic, "Time To Turn," helps remember indexing order. This is essential for any turret numbering quiz or cnc machining quiz to ensure you load the right tool each time.

  2. Absolute vs. Incremental Programming (G90/G91) -

    Master the distinction between G90 (absolute programming) and G91 (incremental programming) with a sample: G90 X50 Y25 moves to coordinates X50, Y25 from the program zero, while G91 X10 Y5 moves 10 units in X and 5 in Y from the current position. Knowing which mode you're in is a common focus in absolute programming questions. Remember "A then I" (Absolute first, Incremental inside) to avoid missteps.

  3. Spindle Speed & Feedrate Formulas -

    Calculate RPM using the formula RPM = (SFM × 3.82)/D, where SFM is Surface Feet per Minute and D is tool diameter in inches. Then derive feed rate (IPM) by multiplying RPM by the number of teeth and chip load per tooth. These formulas are staples in any cnc test or cnc machine programming test for optimizing surface finish and tool life.

  4. Coolant Codes and Best Practices -

    Use M08 for flood coolant, M07 for mist, and M09 to turn coolant off - key entries in a cnc programming quiz. Select the right coolant type (water-soluble or oil-based) based on material thermal conductivity, as recommended by SME guidelines. A quick tip: "Zero Nine Stops the Shine" helps you recall M09 stops all coolant functions.

  5. Work Offsets & Tool Length Offsets -

    Familiarize yourself with G54 - G59 work coordinate systems to program multiple fixtures in one setup. Input tool length offsets via H codes and confirm with a tool probe measurement routine, as outlined by university-level manufacturing courses. The phrase "Five Four Saves Floor" can remind you that G54 is often the primary offset for part zero.

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