Aluminum is soft and fast-cutting, but it’s sticky — it welds to the tool and packs into the flutes. The best end mills for aluminum are built to evacuate chips and resist galling, almost the opposite of steel tooling.
What works in aluminum
- Fewer flutes (2 or 3) — big flute valleys give the large, fast-forming aluminum chips room to escape, preventing packing.
- Polished or uncoated flutes — a mirror polish (or aluminum-specific coatings like ZrN) keeps aluminum from sticking; standard steel coatings can promote built-up edge.
- High helix and sharp positive rake — a 35–45° helix shears cleanly and lifts chips up and out.
- Speed — aluminum tolerates very high spindle speeds and feed rates, which is how it gets that bright finish.
Most aluminum tool failures come from recutting chips that didn’t clear, so use air blast or flood coolant and aggressive feeds to keep the flutes clean.
Frequently asked questions
How many flutes for aluminum? Two or three, for chip clearance.
Should aluminum end mills be coated? Polished/uncoated or aluminum-specific coatings; avoid standard steel coatings.
Why does aluminum stick to my tool? Built-up edge from too-low speeds or the wrong coating — go faster and use polished flutes.