Single-flute carbide end mill
Carbide holds its edge against aluminium's abrasion, and a single flute leaves room for the gummy chip to clear before it re-welds into the cut.
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How to cut aluminium on a CNC router
The three things that matter most:
- Use a single- or two-flute carbide end mill and keep the depth of cut shallow - a common starting ceiling is half the cutter diameter, never a thick single pass.
- Lower the spindle RPM so you make chips, not powder, and feed fast enough that the cutter never rubs. Powder means it is rubbing and about to load up and snap.
- Lubricate and clear chips - a mist, WD-40 or alcohol plus an air blast - so aluminium chips do not re-weld into the cut.
Feeds & speeds calculator, pre-filled for aluminium
Set your cutter diameter, flutes and RPM and read the feed rate and chip load. This is the same tool as the aluminium feed & speed page, which carries the full chip-load reference table.
Recommended feed rate
180.0IPM4,572 mm/min
Plunge rate
45.0 IPM
1,143 mm/min
Chip load
0.1270 mm
0.0050″ / tooth
Chip load bandIn range
0.102 mm0.152 mm
Your chip load is 0.1270 mm per tooth, which is within the recommended 0.102–0.152 mm range for aluminium with a 6.35 mm upcut spiral.
Table range for aluminium at 6.35 mm0.102–0.152 mm
Depth factor (cut is 0.47× diameter)×1.000
Geometry factor (upcut spiral)×1.00
Feed = 18,000 × 2 × 0.1270 mm4,572 mm/min
Aluminium. On a desktop router aluminium is limited by machine rigidity long before it is limited by the chart. Take shallow passes, keep the chip load up, and use a lubricant - dry cutting builds up on the flutes and snaps the tool.
Upcut spiral. The baseline the published charts assume. Chips are lifted clear of the cut, which keeps heat out of the workpiece at the cost of tear-out on the top surface.
Which bit to use
Aluminium is gummy, so chip clearance beats flute count. A single- or two-flute carbide end mill leaves room for the chip to escape; three- and four-flute cutters pack the flutes and re-weld chips in a hobby setup. Carbide holds its edge against aluminium's abrasion far better than HSS. Purpose-made 'aluminium-cut' or 'ZrN/TiB2-coated' single-flutes exist for exactly this.
Feeds, speeds & depth of cut
The rule that catches everyone: lower the RPM. Aluminium wants a real chip to carry heat away, and at a hobby router's high spindle speeds the chip goes to powder and the cutter rubs, overheats and welds. Drop the RPM and keep the feed up so each tooth takes a proper bite. Chip loads are small - researched starting figures land roughly in the 0.02-0.08 mm/tooth range depending on cutter size - but treat that as a starting window and get the exact figure for your cutter and RPM from the calculator, which is pre-filled for aluminium below.
Workholding
Rigidity is everything with aluminium, because the material fights back. Clamp hard, use a vacuum for thin sheet, and back the work so it cannot ring or lift. Any movement side-loads the cutter and snaps it - the same 'breaks on curves' failure the troubleshooting pages describe, amplified in metal.
Chip evacuation & cooling
Chip evacuation and cooling are not optional in aluminium. A hot chip left in the slot re-welds to the tool and the workpiece, which spikes cutting force and breaks the bit. Use a lubricant - a fine mist, WD-40, or even isopropyl alcohol - and an air blast to lift chips clear. This is the difference between a clean cut and a welded, snapped cutter.
Reading your results
Read the chip. Fine silver powder means the chip load is too low and the cutter is rubbing - raise the feed or lower the RPM. Bright, curled chips that eject cleanly mean you are cutting, not rubbing. A blue or straw tint, or chips welding to the tool, means too much heat - more lubricant, more air, or a lighter cut.
Common mistakes
- Running the spindle flat-out: high RPM makes powder, heat and welded chips. Lower it.
- One deep pass through thick stock - aluminium punishes this hardest; take shallow passes.
- No lubricant or air: the chips re-weld and take the bit with them.
- Under-built workholding: aluminium's cutting forces move a part a wood setup would hold.
Tooling & parts for aluminium
The consumables a fix like this usually calls for. Prices are live; we may earn a commission on a purchase, which never affects what we recommend.
In stock
Frequently asked
- Can I cut aluminium on a hobby CNC router?
- Yes, within limits. A light router cuts aluminium with a single-flute carbide bit, shallow passes, lower RPM to make real chips, lubricant and an air blast - but rigidity is the ceiling. A flexible machine chatters and loses steps in metal where a heavier, closed-loop machine does not, so this is as much a machine question as a technique one. See the machines ranked for metal.
- Why is my aluminium cutting as powder instead of chips?
- The spindle RPM is too high for the feed, so each tooth shaves a sliver too thin to be a chip. Powder means the cutter is rubbing, not cutting - it overheats and the fine debris welds into the flutes. Lower the RPM and keep the feed up so the chip thickens into something that carries the heat out.
- What aluminium alloy is easiest to cut?
- 6061 is the standard, well-behaved choice and what most tutorials assume. 7075 and 2024 are stronger aerospace alloys that cut differently and are less forgiving; unless you need their properties, 6061 is the alloy to learn on.
Related
Feed & speed for aluminium (the tool) →Bit breaking →Chatter & vibration →CNC routers ranked for metal →All material guides →
Tooling and technique are drawn from manufacturer documentation and established references; starting ranges are exactly that - the exact feed and chip load for your cutter come from the calculator above, never invented here.