What is surface speed (cutting speed) in machining?

Surface speed (also called cutting speed) is how fast the cutting edge moves relative to the workpiece surface, usually given in metres per minute (m/min) or surface feet per minute (SFM). It is the starting point for every speeds-and-feeds calculation because it depends mainly on the material pair, not on your machine.

How do I calculate spindle RPM from surface speed?

Spindle speed in RPM = (surface speed × 1000) ÷ (π × diameter), with surface speed in m/min and diameter in mm. In inch units the equivalent is RPM = (SFM × 3.82) ÷ tool diameter in inches. As the diameter gets smaller the RPM must rise to keep the same surface speed.

What is feed rate and chip load?

Chip load (feed per tooth) is how much material each flute removes in one revolution. Feed rate = chip load × number of flutes × RPM for milling, or feed per revolution × RPM for turning. Feed rate is what your machine actually moves at, in mm/min or inch/min.

Are these speeds and feeds safe to run in production?

They are conservative starting reference values drawn from common machining handbooks. Real cutting data depends on your tool coating, coolant, machine rigidity and depth of cut. Always confirm against your tooling manufacturer's recommendation and your own shop tests before committing to a production run.

Speeds & Feeds Calculator

Cutting parameters

Operation

Material

Tool diameter

Units

Flutes

Chip load / tooth

Calculated locally in your browser. Reference values only — confirm against your tooling maker's data.

Result

Surface speed— Spindle speed— Chip load— Feed rate—

RPM = (Vc × 1000) ÷ (π × D). Feed rate = chip load × flutes × RPM (milling) or feed/rev × RPM (turning). Values are rounded for the shop floor.

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Reference

How spindle speed and feed rate are calculated

Surface speed (cutting speed) is the speed of the cutting edge relative to the workpiece, set mainly by the material pair. Each material in the calculator carries a conservative reference surface speed in metres per minute.

The RPM formula

RPM = (Vc × 1000) ÷ (π × D)

where Vc is surface speed in m/min and D is diameter in mm. In inch units the same relation is RPM = (SFM × 3.82) ÷ D. Notice the inverse link: a smaller tool must spin much faster to keep the same surface speed.

Feed rate

For milling, feed rate = chip load (per tooth) × number of flutes × RPM. For turning, feed rate = feed per revolution × RPM. Feed rate is the speed your machine actually moves along the cut, in mm/min or inch/min.

Reference surface speeds used here

Material	Vc (m/min)	Approx. SFM
Aluminum (6061-T6)	200	656
Brass / Bronze	150	492
Copper	120	394
Acrylic / Delrin (POM)	120	394
Mild / Low-carbon steel	60	197
Stainless steel (304/316)	35	115
Titanium (6Al-4V)	30	98
Tool steel / Hardened	25	82

These are conservative starting points from common machining handbooks, not a substitute for your tooling manufacturer's recommendation or your own shop testing. Machine rigidity, coolant, coating and depth of cut all shift the safe window.

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