Best End Mills and Router Bits for Cutting Aluminium on a CNC Router

Aluminium is the material that separates a CNC router from a toy. It cuts beautifully with the right tool and the right numbers, and it destroys cutters and parts with the wrong ones. This guide covers tool selection; for workholding, lubrication and the practical side of cutting sheet, read Adam's Tips: Cutting Aluminium Sheet.

The one rule: chips must leave the cut

Aluminium is soft and gummy. If a chip stays in the flute for a second too long it heats up, welds itself to the cutting edge and the tool stops cutting and starts rubbing. Everything about choosing an aluminium cutter comes back to chip evacuation: fewer flutes, polished flutes, a slippery coating, and feeds that make a real chip rather than dust.

Flute count: 1, 2 or 3?

• Single flute is the router cutter for aluminium. One huge flute means the chip always has room to leave, so you can feed hard on a machine that is not especially rigid. The 1 flute DLC up cut is our best selling aluminium bit for exactly this reason, and the CARBiTOOL single flute is the budget alternative on a 6.35mm shank.
• Two flute balances chip room and finish. Use it for slotting and pocketing on a stiffer router or a mill: 2 flute DLC or 2 flute uncoated.
• Three flute is the finishing and side-milling cutter. More edges mean a better wall finish and a stiffer tool, with just enough chip room for aluminium. 3 flute DLC for a mirror wall, 3 flute uncoated for general work, and the WINSTAR range for production shops.

Four flutes are for steel. In aluminium they pack up and weld.

Coated or uncoated?

Uncoated carbide has the sharpest edge straight off the grinder and is the cheapest. For occasional aluminium work it is fine.

DLC (diamond-like carbon) is the coating for aluminium. It is very hard and very slippery, so chips do not stick, the edge lasts several times longer and you can run faster before the finish drops off. If you cut aluminium every week, DLC pays for itself quickly.

TiSiN / TiAlN coatings are for steel. They are designed for heat and have a slightly rounded edge, which is exactly what aluminium does not want. Keep those for the steel end mills.

Which tool for which job

Feeds and speeds for aluminium on a router

Routers spin fast and aluminium wants a real chip, so the answer is almost always "feed faster than feels comfortable". Starting points for a 6mm single flute DLC at 18,000rpm: 1,500 to 2,500mm/min, 1mm to 2mm depth per pass, and air blast or a mist of cutting fluid to keep chips moving. Every size on our product pages has a tested starting feed; the maths behind it is in the Feeds & Speeds Guide.

The symptoms to watch: a high pitched squeal means you are rubbing, not cutting (feed faster or drop RPM); a chip stuck to the tip means it got hot (more air, more feed, fewer passes); chatter on the wall means too much stickout or too deep a cut.

Three things that matter as much as the cutter

1. Collet quality. Runout shows up in aluminium as a rough wall and short tool life. A precision ER collet is cheaper than a tool.
2. Workholding. Aluminium sheet lifts and vibrates. Tape and glue, a vacuum table, or clamps on every edge; tabs alone are rarely enough.
3. Lubrication. A mist system or even WD-40 from a spray bottle makes a bigger difference in aluminium than any other material. Dry cutting is possible with DLC and a single flute, but it is the hard way.

Questions about a specific job? Call Adam on 0448 431 833, or browse the full end mill range.