.calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 0 auto;
padding: 20px;
background-color: #f9f9f9;
border: 1px solid #e0e0e0;
border-radius: 8px;
}
.calc-box {
background: #ffffff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 6px rgba(0,0,0,0.1);
margin-bottom: 40px;
}
.calc-title {
font-size: 24px;
font-weight: bold;
margin-bottom: 25px;
color: #2c3e50;
text-align: center;
border-bottom: 2px solid #3498db;
padding-bottom: 10px;
}
.input-group {
margin-bottom: 20px;
}
.input-group label {
display: block;
font-weight: 600;
margin-bottom: 8px;
color: #34495e;
}
.input-group input, .input-group select {
width: 100%;
padding: 12px;
border: 1px solid #bdc3c7;
border-radius: 4px;
font-size: 16px;
box-sizing: border-box;
}
.input-group select {
background-color: #f8f9fa;
}
.calc-btn {
width: 100%;
padding: 15px;
background-color: #2980b9;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background 0.3s;
}
.calc-btn:hover {
background-color: #2c3e50;
}
.result-box {
margin-top: 25px;
padding: 20px;
background-color: #e8f6f3;
border: 1px solid #a3e4d7;
border-radius: 4px;
text-align: center;
display: none;
}
.result-value {
font-size: 32px;
font-weight: bold;
color: #16a085;
margin: 10px 0;
}
.result-label {
font-size: 14px;
color: #7f8c8d;
text-transform: uppercase;
letter-spacing: 1px;
}
.article-content {
color: #333;
line-height: 1.6;
}
.article-content h2 {
color: #2c3e50;
margin-top: 30px;
}
.article-content h3 {
color: #2980b9;
}
.spec-table {
width: 100%;
border-collapse: collapse;
margin: 20px 0;
background: #fff;
}
.spec-table th, .spec-table td {
border: 1px solid #ddd;
padding: 12px;
text-align: left;
}
.spec-table th {
background-color: #f2f2f2;
font-weight: bold;
}
.note {
font-size: 0.9em;
background: #fff3cd;
padding: 10px;
border-left: 4px solid #ffc107;
margin: 15px 0;
}
function updatePitch() {
var select = document.getElementById('tapSizeSelect');
var pitchInput = document.getElementById('threadPitch');
var selectedPitch = select.value;
if (selectedPitch) {
pitchInput.value = selectedPitch;
calculateFeedRate();
}
}
function calculateFeedRate() {
var rpm = parseFloat(document.getElementById('spindleSpeed').value);
var pitch = parseFloat(document.getElementById('threadPitch').value);
var resultBox = document.getElementById('resultBox');
var resultDisplay = document.getElementById('feedResult');
var noteDisplay = document.getElementById('feedNotes');
if (isNaN(rpm) || isNaN(pitch) || rpm <= 0 || pitch 0 && pitch > 0) {
// logic flows
} else {
return;
}
}
// Calculation: Feed (mm/min) = RPM * Pitch (mm)
var feedRate = rpm * pitch;
resultDisplay.innerHTML = feedRate.toFixed(2) + " mm/min";
// Logic for Rigid Tapping note
noteDisplay.innerHTML = "Program
in your G-code cycle (e.g., G84).";
resultBox.style.display = 'block';
}
Mastering Metric Tapping Feed Rates in CNC Machining
Correctly calculating the feed rate for tapping operations is one of the most critical aspects of CNC programming. Unlike milling or drilling, where feed rates can be adjusted slightly without catastrophic failure, tapping requires perfect synchronization between the spindle rotation and the Z-axis movement. If these are not perfectly matched, you risk stripping the threads or breaking the tap inside the part.
The Golden Formula
For metric threads, the calculation for feed rate is straightforward because the thread pitch is defined directly in millimeters. The feed rate is simply the speed at which the tool must advance to match the threads it is cutting.
Formula: Feed Rate (mm/min) = Spindle Speed (RPM) × Thread Pitch (mm)
For example, if you are using an M6 tap (which has a standard pitch of 1.0mm) and running your spindle at 500 RPM:
500 RPM × 1.0 mm = 500 mm/min.
Rigid Tapping vs. Floating Tap Holders
Rigid Tapping (Synchronized Tapping): Most modern CNC machines support rigid tapping. The machine controller precisely locks the Z-axis motion to the spindle rotation. For rigid tapping, the calculated feed rate above is exact.
Floating Tap Holders (Tension-Compression): On older machines or non-synchronized setups, a floating holder allows the tap to pull out slightly or compress. While the formula RPM × Pitch is still the target, some machinists program the feed slightly lower (e.g., 95-98%) for the in-feed to allow the tension spring to extend, ensuring the tap drives itself without axial pressure. However, for the calculator above, we provide the mathematically theoretical feed rate required for the thread geometry.
Standard Metric Coarse Pitches
When programming, it is vital to know the standard coarse pitch for your tap size if it is not specified as "Fine." Below is a reference chart for common metric taps.
| Metric Size |
Standard Pitch (mm) |
Tap Drill Size (Standard) |
| M3 | 0.5 | 2.5 mm |
| M4 | 0.7 | 3.3 mm |
| M5 | 0.8 | 4.2 mm |
| M6 | 1.0 | 5.0 mm |
| M8 | 1.25 | 6.8 mm |
| M10 | 1.5 | 8.5 mm |
| M12 | 1.75 | 10.2 mm |
| M16 | 2.0 | 14.0 mm |
Why RPM Matters
While the feed rate depends on the RPM, selecting the correct RPM depends on the material you are cutting (Surface Speed or SFM) and the tap material (HSS vs. Carbide). Always consult your tooling manufacturer's catalog to find the recommended surface speed for your specific material (e.g., Aluminum vs. Stainless Steel), then convert that to RPM before using this calculator to find your specific Feed Rate.