What is Cutting Speed?

Cutting speed, often denoted as Vc or SFM (Surface Feet per Minute), is the speed at which the cutting edge of a tool moves relative to the surface of the workpiece. It is a critical parameter in machining operations like milling, turning, and drilling. Understanding the correct cutting speed ensures optimal tool life, superior surface finish, and efficient material removal rates.

How to Calculate Cutting Speed

The formula for cutting speed depends on whether you are using metric or imperial units:

• Metric Formula: Vc = (π × D × n) / 1000. Where Vc is meters per minute (m/min), D is diameter in millimeters (mm), and n is RPM.
• Imperial Formula: Vc = (π × D × n) / 12. Where Vc is Surface Feet per Minute (SFM), D is diameter in inches, and n is RPM.

Using our Cutting Speed Calculator, you simply need to input the diameter of your tool (or workpiece for turning) and the rotational speed (RPM) to get an instant result.

Importance in Machining

Selecting the wrong cutting speed can lead to various issues. If the speed is too high, the heat generated can cause rapid tool wear or even melt the cutting edge. Conversely, if the speed is too low, it can lead to poor productivity, built-up edge (BUE) on the tool, and a rough surface finish. Factors influencing the choice of speed include the material being cut (e.g., Aluminum vs. Stainless Steel) and the tool material (e.g., Carbide vs. HSS).

Frequently Asked Questions

What is the difference between RPM and Cutting Speed?

RPM (Revolutions Per Minute) is how fast the spindle turns. Cutting speed is how fast the cutting edge actually travels across the material. For the same RPM, a larger diameter tool will have a higher cutting speed than a smaller one.

What is SFM?

SFM stands for Surface Feet per Minute. It is the imperial unit for cutting speed used primarily in the United States. 1 SFM is approximately 0.3048 m/min.