Speeds and Feeds Calculator

Speeds and Feeds for Machining

Spindle speed and feed rate are the two primary cutting parameters for milling, turning, and drilling. Surface speed (SFM) is how fast the tool edge moves relative to the workpiece.

Formulas

$$\text{RPM} = \frac{\text{SFM} \times 12}{\pi \times D}$$ $$\text{Feed} = \text{RPM} \times \text{flutes} \times \text{chip load}$$

$D$ is tool diameter in inches, SFM is surface feet per minute, chip load is inches per tooth, and feed is in inches per minute.

Example: a 0.5 in end mill at 300 SFM with 4 flutes and 0.003 in/tooth chip load gives about 2,292 RPM and 27.5 in/min feed.

Frequently Asked Questions

What is SFM?

Surface feet per minute is the cutting speed at the tool circumference. Material and tool type determine the recommended SFM range.

What is chip load?

Chip load (feed per tooth) is how far the cutter advances per flute per revolution. Too high causes tool breakage; too low causes rubbing and heat.

Why multiply SFM by 12?

The formula converts feet per minute to inches per minute because diameter is in inches: circumference in inches is $\pi D$.

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Speeds and Feeds Calculator

Speeds and Feeds for Machining

Formulas

Frequently Asked Questions

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