1. What is Surface Feet per Minute?

Surface Feet per Minute (SFM) is a unit of velocity used in machining to measure the speed at which a point on the workpiece surface travels past the cutting tool. It's a critical parameter in determining optimal cutting speeds for different materials.

2. How Does the Calculator Work?

The calculator uses the SFM formula:

Where:

• \( Diameter \) — Diameter of the rotating tool or workpiece (inches)
• \( RPM \) — Rotational speed (revolutions per minute)
• \( \pi \) — Mathematical constant (approximately 3.1416)

Explanation: The formula converts rotational speed to linear speed at the surface of the rotating object.

3. Importance of SFM Calculation

Details: Proper SFM is crucial for tool life, surface finish, and efficient material removal. Different materials require different SFM values for optimal machining.

4. Using the Calculator

Tips: Enter the diameter in inches and RPM. Both values must be positive numbers. The calculator will compute the surface speed in feet per minute.

5. Frequently Asked Questions (FAQ)

Q1: Why is SFM important in machining?
A: SFM helps determine the appropriate cutting speed for a material, affecting tool life, surface finish, and machining efficiency.

Q2: How does diameter affect SFM?
A: Larger diameters at the same RPM will produce higher SFM values since the surface travels a greater distance per revolution.

Q3: What are typical SFM values?
A: SFM varies by material: 100-300 for aluminum, 80-150 for mild steel, 30-80 for stainless steel, and 50-100 for cast iron.

Q4: Can I use this for metric units?
A: This calculator uses imperial units. For metric, use meters per minute (MPM) instead of SFM.

Q5: How does SFM relate to tool wear?
A: Excessive SFM causes rapid tool wear, while too low SFM reduces productivity and may cause poor surface finish.