The theory behind Surface Feet per Minute:
1. Every cutter has a Diameter
2. Diameter x 3.14159 (PI) = Distance cutter travels every revolution
3. Distance cutter travels every Revolution x 12 = Distance traveled in Feet. (SF)
4. The chart is Recommending how far your cutter should travel per minute in feet. (SFM)
The theory behind the Feed Rate formula (inches):
1. It is Always calculated in “Inches per Tooth” (in/tooth)
2. For every time a cutter goes around how far should the cutter advance into the material Per
3. The chart is Recommending a Chip Load per Tooth depending on cutter diameter and depth of
4. Chip Load per Tooth x Number of teeth = (Inches per Revolution)
The following chart is Recommended Surface Footage for standard 4-Flute styled endmills. For
aluminum, start somewhere in the middle. For steels start on the bottom side and work your way up.
Always use manufacturers recommended Surface Footage for tooling where applicable.