Beginner-Friendly CNC Program Example Library
Simple G-Code Examples with Easy Explanations
Before running any CNC program, it’s important to understand machine coordinates, tool direction, and safe movements. The examples below are written in simple, industry-standard G-code, suitable for beginners.
Example 1: CNC Program to Move Tool in a Square (Basic Milling)
Purpose
This program helps beginners understand:
- X and Y axis movement
- G00 (rapid move)
- G01 (cutting move)
Program Code
%
O1001 (SQUARE CUT PROGRAM)
G21 (Metric units)
G90 (Absolute positioning)
G17 (XY plane selection)
G00 X0 Y0 (Move to start point)
G00 Z5 (Tool above workpiece)
G01 Z-2 F100 (Cutting depth)
G01 X50 Y0 F200
G01 X50 Y50
G01 X0 Y50
G01 X0 Y0
G00 Z5
M30
%
Explanation
- G21 → Sets units to millimeters
- G90 → Absolute positioning (coordinates from zero point)
- G01 Z-2 → Tool cuts 2mm deep
- The tool moves in a square of 50 × 50 mm
✅ Best for: First CNC milling practice
Example 2: CNC Drilling Program (Single Hole)
Purpose
Learn how to drill a hole using CNC safely.
Program Code
%
O1002 (DRILLING PROGRAM)
G21
G90
G00 X25 Y25
G00 Z5
G01 Z-10 F80
G00 Z5
M30
%
Explanation
- Hole position: X25 Y25
- Hole depth: 10 mm
- F80 → Slow feed for drilling
📌 Tip: Always use slow feed rates for drilling to protect the tool.
Example 3: CNC Linear Cutting (Straight Slot)
Purpose
Understanding straight-line cutting in CNC machining.
Program Code
%
O1003 (STRAIGHT SLOT)
G21
G90
G00 X10 Y10
G00 Z5
G01 Z-3 F100
G01 X80 Y10 F250
G00 Z5
M30
%
Explanation
- Cuts a straight slot from X10 to X80
- Depth of cut = 3 mm
- Good example for learning feed control
Example 4: CNC Circular Motion (G02 / G03)
Purpose
Learn circular cutting (very important skill).
Program Code (Clockwise Circle)
%
O1004 (CIRCULAR CUT)
G21
G90
G00 X50 Y25
G00 Z5
G01 Z-2 F100
G02 X50 Y25 I-25 J0 F200
G00 Z5
M30
%
Explanation
- G02 → Clockwise circular movement
- I & J → Distance from center point
- Used for round pockets and profiles
⚠️ Practice this in simulation first!
Example 5: Simple CNC Lathe Facing Program
Purpose
Basic CNC turning operation (Facing).
Program Code
%
O2001 (LATHE FACING)
G21
G90
G00 X50 Z5
G01 Z0 F150
G01 X0
G00 X60 Z10
M30
%
Explanation
- Removes material from the front face
- X-axis → Diameter
- Z-axis → Length
✅ Best for CNC lathe beginners
Example 6: Safe CNC Program Structure (Best Practice)
Always Follow This Order
1. Units (G20 / G21)
2. Positioning (G90 / G91)
3. Plane selection (G17)
4. Rapid move (G00)
5. Cutting move (G01 / G02 / G03)
6. Tool retract
7. Program end (M30)
This structure prevents:
- Tool crashes
- Wrong cutting depth
- Machine errors
Common Beginner CNC Mistakes (Avoid These)
❌ Forgetting Z-safe height
❌ Using high feed rates
❌ Skipping simulation
❌ Wrong coordinate zero
❌ Not checking tool direction
✔ Always dry-run your program first.
Free Tools to Practice CNC Programming
| Tool Name | Use |
|---|---|
| NC Viewer | Online G-code simulation |
| Fusion 360 | CAD + CAM |
| Mach3 | CNC machine control |
| LinuxCNC | Open-source CNC software |
Final Tip for Beginners
“First understand tool movement, then understand cutting.”
If you master G00, G01, G02, and G03, you already know 70% of CNC programming.