Must-Know Vocabulary and Concepts for CNC Routers (Beginner’s Guide)

Getting started with a CNC router can feel overwhelming. Tutorials and guides are full of unfamiliar terms—feeds and speeds, step-over, spoilboard, G-code. This glossary explains the essential CNC vocabulary and concepts so you can follow tutorials, troubleshoot issues, and get the most out of your machine.

In This Guide

• Why Learning CNC Vocabulary Matters
• CNC Router Basics: Core Terms
• Motion & Positioning Concepts
• Cutting Parameters
• Tool Types & Common Toolpaths
• Workholding & Setup Terms
• Software & Control Concepts
• Common Beginner Pitfalls
• Quick Reference Glossary
• Conclusion & Next Steps

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Why Learning CNC Vocabulary Matters

• Understand tutorials and videos without confusion.
• Avoid costly mistakes that damage tools or material.
• Diagnose issues faster and communicate with other makers.

CNC Router Basics: Core Terms

• CNC (Computer Numerical Control): Automates machine tools using computer instructions.
• G-code: The language that tells the CNC how to move, how fast, and when to cut.
• Axes (X, Y, Z): X = left/right, Y = front/back, Z = up/down.
• Workpiece / Stock: The material you’re cutting.
• Tool / Bit: The cutting tool in the spindle that removes material.

Motion & Positioning Concepts

• Home / Homing: The machine’s reference point (machine zero), usually set with limit switches.
• Work Zero (Origin): Your defined start point on the stock (often front-left, top surface).
• Jogging: Manually moving the spindle via controller software.
• Step-over: Lateral distance between adjacent toolpaths during pocketing/3D carving.
• Step-down (Depth of Cut): Vertical depth removed per pass.

Cutting Parameters

• Feeds and Speeds: Balance of spindle RPM (bit rotation speed) and feed rate (travel speed). Correct values prevent burning and broken bits.
• Plunge Rate: Speed at which the bit descends into material.
• Chip Load: Thickness of material removed by each cutting edge per revolution; key to clean, cool cutting.

Tool Types & Common Toolpaths

Common CNC Router Bits

• Flat End Mill: Square tip for pockets, contours, sharp edges.
• Ball Nose End Mill: Rounded tip for smooth 3D carving.
• V-Bit: Angled tip for engraving, lettering, and inlays.

Common Toolpaths

• Profile Cut: Follows the outline of a shape.
• Pocket Cut: Clears material within a boundary.
• Relief Carving: 3D surface carving with varying depth.

Workholding & Setup Terms

• Spoilboard: Sacrificial layer under stock to protect the machine bed (often MDF).
• Clamps: Mechanical hold-downs gripping the material edges.
• Vacuum Table: Uses suction to keep material flat (popular on larger machines).
• Double-Sided Tape / CA Glue + Tape: Common method for small parts without clamps.
• Toolpath Simulation: CAM preview of the cut to catch mistakes before pressing start.

Software & Control Concepts

• CAD (Computer-Aided Design): Create/draw parts (e.g., Fusion 360, FreeCAD).
• CAM (Computer-Aided Manufacturing): Generate toolpaths and G-code from CAD.
• Post-Processor: Adapts CAM output to your controller’s requirements.
• Controller Software (G-code Sender): Sends G-code and provides jogging/homing controls (e.g., Candle, UGS, CNCjs).

Typical flow: CAD → CAM → Post-Processor → Controller Software → Machine.

Common Beginner Pitfalls

• Zeroing Confusion: Mixing up machine zero and work zero causes offsets/crashes.
• Over-aggressive Step-down: Deep cuts without proper feeds/speeds break bits.
• Ignoring Chip Load: Too shallow/slow overheats tools and burns wood.
• Poor Workholding: Stock movement ruins jobs; secure it well.
• Skipping Simulation: Not previewing toolpaths leads to collisions and scrap.

Quick Reference Glossary

Conclusion & Next Steps

Mastering the language of CNC—feeds and speeds, step-over, spoilboard, G-code—makes every part of the process easier. Use this glossary as a quick reference while you practice and your confidence will grow rapidly.