End Mill for Aluminum: Square vs Corner Radius, Flute Count

What makes an end mill right for aluminum?

An end mill is right for aluminum when its flutes can throw big, soft chips out faster than the cutter makes them. Aluminum chips are long and gummy. If they stay in the flute, they get cut again, heat up and weld to the edge, and the end mill snaps. Four features stop that:

• Few flutes. Two or three, so each gap between the cutting edges is wide.

• High helix. A 45° spiral lifts chips up and out of the cut. General-purpose end mills sit nearer 30°.

• Solid carbide. Carbide holds an edge at the high RPM aluminum wants.

• The right coating. ZrN (zirconium nitride) or bare polished carbide. Skip AlTiN and TiAlN: they contain aluminum, and aluminum chips stick to them.

Every end mill in our end mills for aluminum collection ticks all four. They also cut brass, copper and other non-ferrous metals. If you are grinding aluminum by hand instead of milling it, the same chip problem applies to burrs; see carbide burrs for aluminum.

How to read an end mill label

An end mill label lists four sizes and two features, always in the same order. Take 3/8" x 1" x 2-1/2" .020r 3-Flute:

Square end mill or corner radius end mill: which should you buy?

Buy a square end mill only when the part needs a sharp 90° inside corner where the floor meets the wall. For everything else, buy a corner radius end mill. The sharp tip of a square end mill is the thinnest, hottest part of the tool, so it chips first. A small radius thickens that tip and spreads the load.

Pick a square end mill when a drawing calls for a sharp corner, or a square part has to sit flat in the pocket. Pick a corner radius end mill when the drawing allows any fillet, which on most fab-shop brackets, plates and fixtures it does.

Machinists also call a corner radius end mill a bull nose end mill. It is not a corner rounding end mill. A corner radius end mill is a normal end mill with rounded tips. A corner rounding end mill is a profile cutter that puts a round-over on the outside edge of a part. We stock the first kind, not the second.

2 flute or 3 flute end mill for aluminum?

Use a 3 flute end mill for most aluminum work and keep a 2 flute end mill for full-width slots and dry cutting. The extra flute gives a stiffer core, a better finish and a faster feed. The 2 flute gives the widest chip gap, which matters when the cutter is buried on both sides.

Four flutes and up belong on steel. On aluminum the gaps pack with chips in seconds. On our square end mills, flute count rarely changes the price: 2 and 3 flute cost the same in 22 of 27 sizes, so buy the flutes the job needs.

What length end mill do you need?

You need the shortest end mill that reaches the bottom of your deepest cut. Every extra inch of stick-out makes the tool bend more, chatter more and break sooner. We stock each diameter in three lengths:

• Stub: length of cut about 1 to 2 times the diameter. Stiffest. Best for shallow pockets and finish passes.

• Regular: about 2 to 3 times the diameter. The everyday length.

• Long: about 3 to 6 times the diameter. For deep walls. Take lighter cuts.

On our corner radius end mills, the radius comes with the length. Up to 1/2 in., stub lengths carry a .010 in. radius, regular lengths .020 in. and long lengths .040 in. At 5/8 and 3/4 in., stubs are .020 in. and regular and long are .040 in. So if a drawing calls for a .040 in. fillet on a 1/4 in. end mill, the cutter is the long one.

Every end mill for aluminum we stock, by size

We stock 103 Titan USA carbide end mills for aluminum, from 1/8 to 1 in. in diameter. Each row below is one diameter and length. Prices are per end mill. A few small sizes have a 2- or 4-piece minimum, shown in brackets.

Prices per end mill from our catalog, October 26, 2026. Shank diameter equals cutting diameter on every SKU. All are ZrN coated with a 45° helix.

Our picks for common fab-shop jobs

Prices per end mill from our catalog, October 26, 2026.

How fast should you run a carbide end mill in aluminum?

Run a carbide end mill in aluminum as fast as your spindle allows, up to about 800 surface feet per minute as a starting point. The RPM formula is the same one in our drill speed chart: RPM = 3.82 × SFM ÷ diameter in inches.

Most manual knee mills top out well below those numbers on anything under 5/8 in. That is fine. Run at the mill's top speed and keep the feed steady so the end mill cuts a real chip instead of rubbing. Rubbing is what heats aluminum and welds it to the flutes. Three habits help on any machine:

• Lube or air. A mist, a brush of cutting fluid or WD-40, or a steady air blast to clear chips.

• Ramp in. Enter the cut on a ramp or from the side instead of plunging straight down.

• Climb mill on rigid machines. On a manual mill with backlash, conventional milling is safer.

Can you use an end mill without a milling machine?

You can use an end mill in a CNC router, but not in a drill press or a hand drill. A drill press is built for straight-down force. Side cutting loads the bearings sideways, can work the chuck off its taper and throws parts that are only held by hand.

A CNC router with a 1/4 in. or 1/2 in. collet runs our 1/4 and 1/2 in. end mills well in aluminum: use a 2 flute, take light passes and clamp the part hard. Without a mill or router, drill a row of holes and finish the edge with a file or an aluminum cut burr. For holes, see how to choose drill bits for metal.

Will these end mills cut steel?

No. Our end mills for aluminum are made for aluminum, brass, copper and other non-ferrous metals. Steel needs a different end mill: more flutes, a lower helix and a heat-resistant coating such as AlTiN. We don't sell a steel end mill online today. Call us if you need one.

From the shop floor

"Read an end mill label like a spec sheet, not a price tag: size, flutes, coating, profile. Those four details decide whether the tool cuts clean or burns out."

David Castro, President, Eldorado Tools

Not sure which end mill fits your mill or your part? Call our team at (833) 4-ETOOLS or email sales@eldoradotools.com with the drawing or the job.

Sources: Titan USA product specifications (helix, coating, corner style, sizes); Eldorado Tools catalog prices, October 26, 2026; RPM formula as in our drill speed chart.

Change log: October 26, 2026, first draft.