Understanding Feeds, Speeds, and Tooling — A Beginner’s Guide
The Three Words Every CNC Operator Should Understand
Ask any CNC operator what makes the difference between a clean cut and a burned edge, and they’ll mention the same three things: feeds, speeds, and tooling.
They might sound technical, but they’re really just the three pillars of every successful cut — how fast the tool moves, how quickly it spins, and what type of cutter you use. Get those right, and everything else follows.
This guide breaks it down in plain English — no complex formulas, just practical advice you can apply straight away.
What Do “Feeds” and “Speeds” Actually Mean?
Feed rate is how fast the tool moves through the material — measured in millimetres per second or metres per minute.
Spindle speed (or RPM) is how fast the tool spins.
Think of them like walking and breathing. You can move quickly or slowly, but both need to stay in balance. If your feed rate is too slow compared to your RPM, the cutter spins too long in one spot, heating up and burning the material.
If it’s too fast, the cutter bites off more than it can handle — causing chatter, poor finish, or even tool breakage.
Quick Tip: If your cuts are smoky or scorched, slow down your spindle speed or increase your feed rate. The tool is rubbing, not cutting.
What Do “Feeds” and “Speeds” Actually Mean?
Feed rate is how fast the tool moves through the material — measured in millimetres per second or metres per minute.
Spindle speed (or RPM) is how fast the tool spins.
Think of them like walking and breathing. You can move quickly or slowly, but both need to stay in balance. If your feed rate is too slow compared to your RPM, the cutter spins too long in one spot, heating up and burning the material.
If it’s too fast, the cutter bites off more than it can handle — causing chatter, poor finish, or even tool breakage.
Quick Tip: If your cuts are smoky or scorched, slow down your spindle speed or increase your feed rate. The tool is rubbing, not cutting.
Tooling — Choosing the Right Cutter for the Job
Tooling choice is just as important as machine setup. The right cutter type, flute count, and coating all affect finish quality and tool life.
A few basics:
Up-cut bits: Pull chips upward, great for deeper cuts but can cause tear-out on top surfaces.
Down-cut bits: Push chips downward, giving cleaner top edges but needing slower feed rates.
Compression bits: Combine both — ideal for veneered panels or laminates.
Single-flute bits: Great for plastics and aluminium where chip clearance is key.
Two-flute bits: The go-to choice for most woods and MDF.
Each tool has its “happy place” — get the right one and even tough materials cut beautifully.
Pro Tip: If your edges are fuzzy or chipped, try a sharper down-cut or compression bit, and always make sure your collet is clean and tight.
Tooling — Choosing the Right Cutter for the Job
Tooling choice is just as important as machine setup. The right cutter type, flute count, and coating all affect finish quality and tool life.
A few basics:
Up-cut bits: Pull chips upward, great for deeper cuts but can cause tear-out on top surfaces.
Down-cut bits: Push chips downward, giving cleaner top edges but needing slower feed rates.
Compression bits: Combine both — ideal for veneered panels or laminates.
Single-flute bits: Great for plastics and aluminium where chip clearance is key.
Two-flute bits: The go-to choice for most woods and MDF.
Each tool has its “happy place” — get the right one and even tough materials cut beautifully.
Pro Tip: If your edges are fuzzy or chipped, try a sharper down-cut or compression bit, and always make sure your collet is clean and tight.
How to Find the Right Settings (Without Guessing)
Every material behaves differently — MDF can take aggressive cuts, while acrylic or aluminium need finesse. The goal is to remove as much material as possible per revolution without stressing the tool.
Start with recommended settings from your tooling supplier — companies like LMT Tools and others provide reliable charts for different materials. Then adjust in small steps:
- Increase feed rate if the chips are too fine (you’re rubbing).
- Decrease feed rate or RPM if you’re chipping edges or hearing chatter.
- Listen — a smooth, steady tone means you’re close to ideal.
Workshop Wisdom: The sound of a good cut is unmistakable — consistent and confident, not screaming or rattling.
The Role of Chip Load
Chip load is simply how much material each cutting edge removes per revolution. It’s the link between feed rate, spindle speed, and flute count.
Too low a chip load = friction and heat. Too high = tool overload. You don’t need to calculate it exactly — just understand what it means.
For most 6–9kW spindles cutting MDF or ply:
- A 6mm bit might run around 18,000–22,000 RPM
- Feed rate around 6–9 metres/minute
- Depth of cut about 3–6mm per pass
Small adjustments make a big difference — once you find the sweet spot, stick with it for consistent results.
How to Find the Right Settings (Without Guessing)
Every material behaves differently — MDF can take aggressive cuts, while acrylic or aluminium need finesse. The goal is to remove as much material as possible per revolution without stressing the tool.
Start with recommended settings from your tooling supplier — companies like LMT Tools and others provide reliable charts for different materials. Then adjust in small steps:
- Increase feed rate if the chips are too fine (you’re rubbing).
- Decrease feed rate or RPM if you’re chipping edges or hearing chatter.
- Listen — a smooth, steady tone means you’re close to ideal.
Workshop Wisdom: The sound of a good cut is unmistakable — consistent and confident, not screaming or rattling.
The Role of Chip Load
Chip load is simply how much material each cutting edge removes per revolution. It’s the link between feed rate, spindle speed, and flute count.
Too low a chip load = friction and heat. Too high = tool overload. You don’t need to calculate it exactly — just understand what it means.
For most 6–9kW spindles cutting MDF or ply:
- A 6mm bit might run around 18,000–22,000 RPM
- Feed rate around 6–9 metres/minute
- Depth of cut about 3–6mm per pass
Small adjustments make a big difference — once you find the sweet spot, stick with it for consistent results.
The Payoff of Getting It Right
When feeds, speeds, and tooling align, you get clean edges, faster cycles, longer tool life, and quieter operation.
It’s the difference between fighting the machine and working with it.
And the best part? Once you develop an ear for it, you’ll instinctively know when a cut is right — it’s one of the most satisfying skills in CNC machining.
Common Mistakes and How to Avoid Them
Cutting too slow → burns, dull bits, poor finish
Cutting too fast → chatter, breakage, inaccurate cuts
Wrong tool for material → tear-out or melting
Loose collet or worn tool holder → vibration and poor precision
Ignoring chip evacuation → re-cutting debris and heat build-up
These issues are easy to avoid once you recognise the signs. A few seconds of adjustment can save hours of sanding or rework.
Final Thoughts From the Workshop Floor
Understanding feeds, speeds, and tooling isn’t about memorising numbers — it’s about feeling how your machine interacts with the material.
The more you experiment, listen, and learn, the more natural it becomes.
A CNC router isn’t just a machine — it’s a conversation between tool, material, and operator. The more you listen, the better the results.