Please enter valid positive numbers for all fields.
Feed Rate (Imperial):0 IPM
Feed Rate (Metric):0 mm/min
Feed Per Revolution (IPR):0.0000 in/rev
function calculateFeed() {
// 1. Get DOM elements
var rpmInput = document.getElementById('spindleRpm');
var flutesInput = document.getElementById('numFlutes');
var chipLoadInput = document.getElementById('chipLoad');
var errorDiv = document.getElementById('errorDisplay');
var resultsDiv = document.getElementById('results');
var resIpm = document.getElementById('resIpm');
var resMm = document.getElementById('resMm');
var resIpr = document.getElementById('resIpr');
// 2. Parse values
var rpm = parseFloat(rpmInput.value);
var flutes = parseFloat(flutesInput.value);
var chipLoad = parseFloat(chipLoadInput.value);
// 3. Validation
if (isNaN(rpm) || rpm <= 0 || isNaN(flutes) || flutes <= 0 || isNaN(chipLoad) || chipLoad <= 0) {
errorDiv.style.display = 'block';
resultsDiv.style.display = 'none';
return;
}
// 4. Hide error
errorDiv.style.display = 'none';
// 5. Calculation Logic
// Formula: IPM = RPM × Flutes × Chip Load
var feedRateIPM = rpm * flutes * chipLoad;
// Formula: Feed Per Revolution (IPR) = Flutes × Chip Load
var feedPerRev = flutes * chipLoad;
// Metric Conversion: 1 inch = 25.4 mm
var feedRateMetric = feedRateIPM * 25.4;
// 6. Display Results
resIpm.innerHTML = feedRateIPM.toFixed(2) + " IPM";
resMm.innerHTML = feedRateMetric.toFixed(1) + " mm/min";
resIpr.innerHTML = feedPerRev.toFixed(4) + " in/rev";
resultsDiv.style.display = 'block';
}
Understanding Drilling Feed Rates
Calculating the correct feed rate is critical for CNC machining and manual drilling operations. The feed rate determines how fast the drill bit advances into the material. Setting this correctly ensures optimal tool life, surface finish, and efficient chip evacuation.
The Core Formulas
The primary metric used in the United States for feed rate is Inches Per Minute (IPM). To calculate this, you need to understand the relationship between your spindle speed, the number of cutting edges (flutes), and the chip load.
Feed Rate (IPM) = RPM × Number of Flutes × Chip Load
Where:
RPM: Revolutions Per Minute of the spindle.
Number of Flutes: Usually 2 for standard twist drills, but can vary for high-performance tooling.
Chip Load: The thickness of material removed by each cutting edge per revolution (also known as Feed Per Tooth).
Why Chip Load Matters
Chip load is often the most important variable to control. If the chip load is too small (rubbing), the tool will generate excessive heat and dull quickly. If the chip load is too high, the tool may break due to excessive force. Most tool manufacturers provide recommended chip load data based on the drill diameter and the material being cut (e.g., Aluminum vs. Stainless Steel).
IPM vs. IPR
While CNC machines often run on IPM (Inches Per Minute), many manual machinists and lathe operators prefer IPR (Inches Per Revolution). IPR is simply the distance the drill advances in one full rotation.
IPR = Chip Load × Number of Flutes
This calculator provides both metrics simultaneously to accommodate different programming styles and machine requirements.
Tips for Optimizing Feed Rates
Start Conservatively: When testing a new material, start at the lower end of the manufacturer's recommended surface footage and chip load.
Watch the Chips: In drilling, chips should be consistent and evacuated smoothly. If you see powder or smoke, your feed may be too low (rubbing). If chips are thick and discolored (blue/purple in steel), heat generation is high.
Deep Hole Drilling: For holes deeper than 3x or 4x diameter, consider using a peck cycle to break chips and allow coolant to reach the tip.