Speeds and feeds

Pick the workpiece and tool materials, slide the cutting speed between the conservative and aggressive ends of the range (or type your own SFM or m/min), set your machine’s top spindle speed, then choose an operation. Inch and metric are switchable; values convert when you switch.

Spindle speed: RPM = SFM × 12 / (π × D) in inches, or RPM = Vc × 1000 / (π × D) in millimetres. If that exceeds the machine’s maximum, the spindle is capped and feed is worked out at the capped speed (the cut simply runs slower than ideal).
Milling: feed = RPM × flutes × feed per tooth. The default chip load scales with tool diameter from a ½″ reference value per material. With radial engagement (ae) under half the diameter the chip is thinner than the programmed feed, so feed per tooth can rise by 1 / √(1 − (1 − 2·ae/D)²) — the radial chip-thinning factor — to keep a healthy chip.
Turning: feed per revolution from a per-material roughing value (finishing ≈ 35%, boring ≈ 60%); MRR = 12 × SFM × feed × depth of cut. Finish estimate: R_max ≈ f² / (8 r).
Drilling: drills run at about 70% of the turning speed, feed ≈ material factor × diameter per rev; reamers at about half the drill speed and twice the feed. Peck past about 3×D.
Tapping: feed per revolution equals the pitch. Speeds are low — about a fifth of the HSS turning speed, more for forming taps.
Power uses unit power (hp per in³/min removed) for the material: about 0.3 for aluminium, 0.9–1.1 for steels, 1.3 for austenitic stainless. Add 20–30% for machine losses and dull tools.

Data sources: cutting-speed ranges and feeds are typical published shop starting points (Machinery’s Handbook ranges and tooling-catalogue values), simplified into one range per material and tool material.

These are starting points — verify with your tooling manufacturer. Rigidity, stick-out, coolant, tool coating and geometry, and machine power all change the right answer. Start at the conservative end and listen to the cut.

Share link copies a URL that opens this tool exactly as you have it set up. It carries the material, tool and cut on every tab. Opening a link replaces your own saved settings for the tool; a Restore my settings button brings them back. To write a link by hand, use mat, tool, units — for example /tools/speeds-feeds/?mat=al-wrought&tool=carbide&units=mm.

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