Understanding Speeds and Feeds
In CNC milling, "Speeds and Feeds" are the two most critical parameters. **Speed** refers to the Spindle Speed (RPM), which is how fast the cutting tool rotates. **Feed** refers to the Feed Rate (IPM), which is how fast the tool moves across the material.
These values are determined by the material being cut and the cutting tool itself. The goal is to find a balance that produces a good surface finish, efficient material removal, and long tool life. The core calculation starts with the material's recommended Surface Feet per Minute (SFM) to find the correct RPM, then uses the Chip Load per tooth to determine the final feed rate.
How to Use the Calculator
- Select the material you are milling. This sets the recommended Surface Speed (SFM).
- Enter the diameter of your cutting tool (end mill).
- Enter the number of flutes (cutting edges) on your tool.
- Enter the recommended Chip Load for your tool and material combination (this value is often provided by the tool manufacturer).
- Click "Calculate" to get the suggested Spindle Speed (RPM) and Feed Rate in Inches Per Minute (IPM).