Breaking Down Feeds and Speeds

How to dial in precision, efficiency, and quality on your CNC router.

If you’ve ever burned wood, broken a bit, or wondered why your cuts aren’t as clean as they should be, there’s a good chance your feeds and speeds need attention. These two settings — how fast the tool spins and how quickly it moves through material — can make or break the quality of your CNC woodworking projects.

At Phantom CNC Systems, we believe understanding feeds and speeds is one of the most important skills for any CNC router operator. Let’s simplify it so you can put it to work in your shop.

What Are Feeds and Speeds?

• Feed Rate – How quickly the cutting tool moves through the material, usually measured in inches per minute (IPM) or millimeters per minute (mm/min).

  
  

• Spindle Speed (RPM) – How fast the tool spins, measured in revolutions per minute.

  
  

These two work together to determine the chip load — the thickness of material removed by each cutting edge per revolution. Getting chip load right is the key to cleaner cuts, longer tool life, and faster production.

Why Chip Load Matters

Chip load affects everything from surface finish to tool wear:

• Too Low – Causes rubbing instead of cutting, leading to heat buildup, burning, and dull bits.

  
  

• Too High – Puts excessive stress on the bit, increasing the risk of breakage and rough cuts.

  
  

• Just Right – Produces clean, efficient chips that carry away heat and reduce wear.

Factors That Affect Feeds and Speeds

• Material Type – Softwoods like pine cut differently than hardwoods like maple, or composites like MDF.

  
  

• Bit Diameter – Larger bits can handle higher feed rates, smaller bits require more finesse.

  
  

• Number of Flutes – Fewer flutes are better for softer materials (bigger chips, less heat), more flutes work well for harder materials.

  
  

• Machine Rigidity – Heavier-duty CNC routers can run more aggressive settings without chatter.

  
  

• Hold-Down Method – Secure workholding allows faster feed rates without shifting or vibration.

How to Calculate Starting Points

Most bit manufacturers provide recommended chip loads for their tooling.

To calculate a starting feed rate:

Formula: Feed Rate (IPM) = Chip Load × Number of Flutes × RPM

Example:

• Chip Load: 0.012"

• Flutes: 2

• RPM: 18,000

• Feed Rate = 0.012 × 2 × 18,000 = 432 IPM

From here, you can fine-tune based on cut quality and sound.

Signs You Need to Adjust

• Burn Marks → Increase feed rate or reduce RPM.

• Frayed Edges → Slow down feed rate or use a sharper bit.

• Bit Breakage → Reduce chip load or switch to a stronger bit type.

• Excessive Noise/Chatter → Adjust speeds, feeds, or improve workholding.

Phantom CNC Pro Tip

Always start with the manufacturer’s recommendation for your specific bit and material, then make small adjustments. Keep a shop log of the settings that work best for your most common materials — it’ll save time and reduce trial-and-error.

Final Thoughts

Mastering feeds and speeds isn’t just about avoiding mistakes — it’s about unlocking the full potential of your CNC router. By understanding how these settings work together, you’ll cut cleaner, extend tool life, and work more efficiently.