1. What is SFM to RPM Conversion?

The SFM (Surface Feet per Minute) to RPM (Revolutions per Minute) conversion calculates the rotational speed needed at the cutting tool's diameter to achieve a specific surface speed. This is essential in machining operations.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( SFM \) — Surface feet per minute (cutting speed)
• \( Diameter \) — Diameter of the cutting tool in inches
• 3.82 — Conversion factor (12/π)

Explanation: The formula converts linear surface speed to rotational speed based on tool diameter.

3. Importance of RPM Calculation

Details: Proper RPM calculation ensures optimal cutting conditions, tool life, and surface finish. Too high RPM can cause tool wear, while too low can result in poor cutting action.

4. Using the Calculator

Tips: Enter SFM (based on material and tool type) and tool diameter in inches. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical SFM range?
A: SFM varies by material: 100-300 for aluminum, 50-150 for steel, 30-80 for stainless steel, and 200-400 for plastics.

Q2: Why is diameter important in RPM calculation?
A: Larger diameters require lower RPM to achieve the same surface speed, as the circumference is greater.

Q3: Can this be used for lathe operations?
A: Yes, the same formula applies to both milling and turning operations.

Q4: What if my tool diameter is in millimeters?
A: Convert mm to inches (divide by 25.4) before using the calculator.

Q5: How does RPM affect chip formation?
A: Proper RPM helps create ideal chip thickness - too low causes rubbing, too high causes heat buildup.