How to Calculate Feed Rate Milling

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Milling Feed Rate Calculator

Calculate the optimal table feed for your CNC or manual milling operations.

Units match your preference (Inches or mm)

Calculated Feed Rate

How to Calculate Milling Feed Rate

In machining, the feed rate is the speed at which the cutting tool moves through the material. Calculating the correct feed rate is critical for tool life, surface finish, and preventing tool breakage. The feed rate is typically measured in Inches Per Minute (IPM) or Millimeters Per Minute (mm/min).

The Feed Rate Formula

The standard formula used in this calculator is:

Feed Rate = RPM × Number of Flutes × Feed Per Tooth

Variables Explained

  • RPM (Revolutions Per Minute): The rotational speed of the spindle. This is determined by the material's recommended Surface Feet Per Minute (SFM) and the tool diameter.
  • Number of Flutes: The number of cutting edges on the milling bit (usually 2, 3, or 4).
  • Feed Per Tooth (Chip Load): The thickness of the material removed by each individual flute during one revolution.

Example Calculation

If you are using a 4-flute end mill in aluminum with the following specs:

  • RPM: 5,000
  • Flutes: 4
  • Chip Load: 0.002 inches

Calculation: 5,000 × 4 × 0.002 = 40.0 Inches Per Minute (IPM).

function calculateFeedRate() { var rpm = parseFloat(document.getElementById('spindleSpeed').value); var flutes = parseFloat(document.getElementById('numFlutes').value); var chipLoad = parseFloat(document.getElementById('chipLoad').value); var resultDiv = document.getElementById('millingResult'); var output = document.getElementById('feedRateOutput'); var label = document.getElementById('unitLabel'); if (isNaN(rpm) || isNaN(flutes) || isNaN(chipLoad) || rpm <= 0 || flutes <= 0 || chipLoad <= 0) { alert("Please enter valid positive numbers for all fields."); resultDiv.style.display = "none"; return; } var feedRate = rpm * flutes * chipLoad; // We round to 3 decimal places for precision in machining var formattedFeed = Number(Math.round(feedRate + 'e3') + 'e-3'); output.innerHTML = formattedFeed; label.innerHTML = "Linear Units per Minute (IPM or mm/min)"; resultDiv.style.display = "block"; }

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