Machining Speed and Feed
Spindle speed (RPM) from surface speed (SFM) and cutter or work diameter.
Example
You enter
- Surface speed (SFM) 100
- Diameter (in: cutter for mill/drill, work for turning) 0.5
- Flutes / teeth (optional, for feed) 2
- Chip load per tooth (in, optional) 0.002
You get
- Spindle speed 764 RPM
- Feed rate 3.056
Checked against published worked examples from: U.S. Navy, Naval Education and Training Command; CNC Concepts, Inc. (Mike Lynch).
Details, formula, and sources
ScopeSpindle speed (RPM) from surface speed (SFM) and cutter or work diameter, plus feed rate (IPM) from the number of flutes and chip load per tooth (first-principles cutting geometry; Machinery's Handbook speeds-and-feeds method).
Formula or tableRPM = 12 * SFM / (pi * dia(in)); feed IPM = RPM * flutes * chip_load(in/tooth); 12/pi = 3.8197.
Source and editionFirst-principles cutting geometry; the speeds-and-feeds method as in Machinery's Handbook (Industrial Press), by name.
Free accessPure geometry, public; the surface speed (SFM) and chip load per tooth are user-supplied from the tool / material chart.
What governsEstimate. AHJ and licensed professional govern.
API field namessurface_speed_sfm, diameter_in, num_flutes, chip_load_in, rpm, feed_ipm
- Chart inputs recommended SFM and chip load per tooth are user-supplied from the tool/material charttool manufacturer data