By Zencalcy Editorial TeamLast reviewed About us
Spindle speed comes from surface footage: RPM = 12 × SFM ÷ (π × diameter). Feed rate then follows from chip load and the number of flutes. Getting both right is the difference between a clean cut and burnt edges or broken tools.
RPM and feed rate for a cutter or drill.
RPM = 12 × SFM ÷ (π × D) Feed = RPM × chip load × flutes
Typical SFM: aluminium 300–600, mild steel 80–120 with HSS, stainless 40–80, hardwood 200–300. Chip load for a ½-inch carbide end mill in aluminium is about 0.005 in per tooth.
| Symbol | Meaning |
|---|---|
| SFM | Surface feet per minute for the material. |
| D | Tool diameter. |
| fz | Chip load per tooth. |
RPM = 12 × 400 ÷ (π × 0.5) = 3,056; feed = 3,056 × 0.005 × 3 = 45.8 in/min.
Continue with the Beam Deflection Calculator, Beam Load Calculator, Bending Stress Calculator, or the Wood Beam Span Calculator — or browse more structural & workshop and all construction calculators.
About 100 with high-speed steel and 300–400 with carbide. Reduce by 30% for stainless.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026