Question 1

How do I calculate CNC feeds and speeds?

Accepted Answer

Calculate spindle speed first: RPM = (SFM × 3.82) / Tool Diameter (inches) or RPM = (Vc × 1000) / (π × D) for metric. Then calculate feed rate: Feed Rate = RPM × Chipload × Flutes (milling), RPM × Feed/Rev (drilling/turning), or RPM ÷ TPI (tapping). SFM depends on the tool material (HSS vs carbide) and workpiece material. Our Feeds and Speeds Calculator auto-fills recommended SFM values for 18 materials, so you just need to select your operation and enter your tool diameter and material type.

Question 2

What is the difference between feeds and speeds?

Accepted Answer

Speed refers to spindle speed (RPM) — how fast the tool or workpiece rotates. Feed refers to feed rate — how fast the tool moves through the material. For milling: Feed Rate = RPM × Chipload × Flutes. For drilling and turning: Feed = RPM × Feed/Rev. For tapping: Feed = RPM ÷ TPI. Getting both right is essential — too much speed creates heat and tool wear; too much feed can break the tool. Our calculator shows both values and lets you adjust either one to find safe cutting parameters.

Question 3

Are these manufacturing calculators free to use?

Accepted Answer

Yes. All manufacturing and machining calculators on Ganak are completely free, with no sign-up required. Calculations run instantly in your browser using industry-standard machining formulas and industry-standard material SFM ranges. No data is ever sent to our servers.

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