Chip load is the thickness of material each cutting edge removes per revolution, measured in inches per tooth. It is the key variable for tool life: too little rubs and work-hardens the cut, too much overloads the edge.

What is the feed-rate formula?

Feed rate in inches per minute equals spindle RPM times the number of flutes times the chip load per tooth. More flutes or a heavier chip load both push the feed rate up at a fixed RPM.

How do I pick a starting chip load?

Use the material presets as a starting point for a roughly quarter-inch end mill, then scale down for smaller diameters and fragile tools. Manufacturer charts for your exact tool and coating are always more precise.

Why back-calculate chip load from feed?

If a known good program runs at a given RPM and feed, dividing back out the chip load tells you the actual load per tooth. That lets you keep the same load when you change RPM or move to a cutter with a different flute count.

Should I reduce chip load for deep or full-width cuts?

Yes. Heavy radial or axial engagement raises cutting forces and heat, so trim the chip load and feed for slotting or deep pockets. Light radial cuts with high-efficiency toolpaths can often run a higher chip load safely.

Feeds & Speeds Calculator

Feed rate is where finish, tool life, and cycle time all meet. Set it from chip load — the bite each flute takes per revolution — rather than guessing, and you get predictable results across cutters and machines. This calculator converts between feed rate and chip load in both directions and offers per-material starting points.

How it works

The core formula multiplies the spindle speed by how many edges cut and how much each one removes:

feed (IPM)      = RPM × flutes × chip load per tooth
chip load (IPT) = feed (IPM) / (RPM × flutes)

Because every flute removes its chip once per revolution, a 4-flute cutter feeds twice as fast as a 2-flute cutter at the same RPM and chip load.

Example and tips

A 4-flute end mill at 4,000 RPM with a 0.003 inch chip load gives a feed of 4000 × 4 × 0.003, or 48 IPM. If you later drop to a 2-flute cutter and want the same load per tooth, the feed must halve to 24 IPM. Keep chip load constant when you change speeds, lighten it for slots and deep cuts, and trust chip appearance — clean, well-formed chips that carry heat away signal a healthy feed.