Download the custom tool library for aluminum here.
What is aluminum?
Aluminum is a lightweight, durable, and corrosion-resistant metal that is electrically conductive. It comes in a vast number of different alloys, each with different physical and thermal properties. Some of these alloys are easily cast, wrought, machined, or extruded. Other alloys are extremely strong, ductile, or resistant to stress cracking. The most commonly used, general-purpose alloy is 6061 aluminum, and it’s our favorite alloy for milling because it’s a great blend of strength and machinability. It’s strong enough to be used for many applications but soft enough to mill.
What is aluminum used for?
Aluminum is used for everything from engine parts to MacBooks to jewelry, soda cans, airplanes, and so much more. The milling machine bed, spoilboard, and Z-carriage are all made of aluminum. It's popular because it’s a great blend of price, strength, and machinability, and it can be anodized to give a premium surface finish.
Is aluminum safe?
Yes. Just make sure you don’t get aluminum dust and chips in your eyes or lungs. We recommend vacuuming after each milling job and in the middle of jobs longer than 30 minutes.
Where can I get aluminum?
We sell precut pieces of 6061 aluminum in our store! They’re the perfect size for many milling machine projects, and they fit nicely on the machining bed. You can also get aluminum from metal suppliers, scrap yards, and even soda cans. Just make sure you know what alloy it is, lest you risk encountering one that's difficult to mill.
What’s the best way to fixture aluminum to the bed of my milling machine?
Aluminum is one of the harder materials in the milling machine’s repertoire, so more force is required to push the tool through the material. This means that proper fixturing is more important than with softer materials like wax or FR-1. If the fixturing isn’t strong enough to resist the higher cutting forces, the material can be knocked loose during milling, which can damage itself, the tool, and even the machine.
For thin, flexible aluminum sheets, it’s important to make sure the material is as flat as possible. If it’s not flat, parts of it may stick up and cause a small tool to cut too deeply. This can break tools or damage the part. We recommend removing all burrs and covering the bottom of the material with double-sided tape to attach it to the bed.
To prevent the material from bending when you remove it from the bed, you can optionally use a sacrificial layer, like FR-1 circuit board, and stick the aluminum to it. Then put tape on the underside of the board and stick the whole thing to the milling machine bed. Be sure to offset your material origin by the thickness of the board.
Aluminum sheet with burrs on the edge that need to be removed.
Aluminum sheet with double-sided tape applied.
Aluminum sheet secured to scrap FR-1, ready to be milled.
For thicker aluminum bar stock, fixturing is even more important because the center of gravity is higher. A heavy-duty tape like high-strength double-sided "Nitto" tape does a great job of keeping the stock from moving. The Precision Fixturing and Toe Clamp Set is another option for thicker pieces of stock. When using tape, we also like to use the alignment bracket because it constrains the movement of the material on two sides, which adds to the effect of other fixturing methods. If you’re feeling ambitious, you can remove the spoilboard, drill holes in the material that align with the slots in the T-slot bed, and then bolt it to the bed with M5 bolts. This provides extremely strong fixturing.
Aluminum bar stock with Nitto tape applied.
Aluminum bar stock secured to the bed with Nitto tape.
Aluminum bar stock secured to the bed with hot glue around the edges.
What end mills should I use when milling aluminum?
Use the biggest tool you possibly can to allow for the fastest material removal and least chance of tool breakage. The easiest tools to use are 1/8" and 1/16" flat or ball end mills. Aluminum is one of the less forgiving materials, and it’s easy to break small tools with too high of a feed rate or inadequate fixturing. The 1/8" and 1/16" tools are very strong, and they can cut away a lot of material at once. That being said, any tool can be used to mill aluminum as long as the settings are correct.
What are some example projects?
Anodized Aluminum Voronoi Pattern Earrings 
Custom Aluminum Rings 
Recommended Feeds and Speeds
To make it easier to use these recommended feeds and speeds, we’ve created a way for you to quickly import into our software all the settings you see listed below. To do this, download the Aluminum Custom Tool Library, which contains all the recommended feeds and speeds for this material. Then open our software, click File > Tool Library, click the “Import” button, and select this file. Before using these settings, it’s a good idea to read through our Feeds and Speeds Guide.
Download the Aluminum Custom Tool Library here.
Note: The feeds and speeds below are optimized for the V2 Othermill. If you're using a Bantam Tools Desktop PCB Milling Machine, Othermill Pro, or Kickstarter Othermill, you may need to experiment to find optimal settings.
Tool: 1/8" flat end mill
Feed rate: 7.087 in/min (180 mm/min)
Plunge rate: 0.591 (15 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.002" (0.05 mm)
Tool: 1/16" flat end mill
Feed rate: 7.087 in/min (180 mm/min)
Plunge rate: 0.591 (15 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.003" (0.08 mm)
Tool: 1/32" flat end mill
Feed rate: 7.087 in/min (180 mm/min)
Plunge rate: 0.591 (15 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.003" (0.08 mm)
Tool: 1/64" flat end mill
Feed rate: 1.417 in/min (36 mm/min)
Plunge rate: 0.157 in/min (4 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.001" (0.02 mm)
Tool: 1/100" flat end mill
Feed rate: 1.417 in/min (36 mm/min)
Plunge rate: 0.157 in/min (4 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.001" (0.02 mm)
Advanced Feeds and Speeds
Warning: These settings are for advanced users. Before using any of the information provided here, you must read the section above on fixturing your material, and you must have a way of precisely measuring your material thickness (we recommend digital calipers). The feeds and speeds specified here are more aggressive (and thus faster), and improperly fixtured material can be knocked loose and damage itself and your machine. Additionally, the material surface needs to be completely flat, or else 1/32", 1/64", and 1/100" end mills will break when they encounter part of the material that's sticking up.
Lastly, if you’re using tools smaller than 1/16", you must make sure that the tool is removing the correct amount of material on the first pass, or else your tool may cut too deep and break. All subsequent passes will be correct, but the first pass can be affected by anomalies like tape thickness, burrs on the material edges, and material warping, all of which can increase the height of the material surface, causing the tool to cut too deep.
Tool: 1/8" flat end mill
Feed rate: 59 in/min (1500 mm/min)
Plunge rate: 5 in/min (127 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.002" (0.05 mm)
Tool: 1/16" flat end mill
Feed rate: 59 in/min (1500 mm/min)
Plunge rate: 5 in/min (127 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.002" (0.05 mm)
Tool: 1/32" flat end mill
Feed rate: 59 in/min (1500 mm/min)
Plunge rate: 5 in/min (127 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.002" (0.05 mm)
Tool: 1/64" flat end mill
Feed rate: 15 in/min (381 mm/min)
Plunge rate: 1 in/min (25.4 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.001" (0.02 mm)
Tool: 1/100" flat end mill
Feed rate: 15 in/min (381 mm/min)
Plunge rate: 1 in/min (25.4 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.001" (0.02 mm)