Brass

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What is brass?

Brass is an alloy of primarily copper and zinc. It’s desirable because it has a gold-like luster and color, a low enough melting point to be easily cast, and low friction. There are many kinds of brass alloys, each with different properties that make it suitable for different uses. Some alloys are very hard; some are different colors, such as silver; some resist corrosion; and some kill bacteria. Our favorite brass is 360 brass, also called free-machining brass because it’s hard enough to hold its shape but soft enough to machine easily.

What is brass used for?

Brass is used in an enormous number of ways: decorative trim, clockwork pieces, antibacterial bed rails, doorknobs, pipe fittings, sculptures and statues, ammunition casings, and spark-safe work areas.

Is brass safe?

Yes, if you don’t breathe or eat the swarf.

Where can I get brass?

We sell pre-cut pieces of 360 brass in our store! They’re the perfect size for many Othermill projects, and they fit nicely on the Othermill bed. You can also find brass in many online metal suppliers.

Fixturing: How do I attach brass to the bed of my Othermill?

Brass is one of the harder materials in the Othermill’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.

Nitto Permacel P-02 tape or hot glue are both good options, and we recommend using them in conjunction with the alignment bracket for extra rigidity.

To use Permacel tape, place strips evenly across the underside of the material. Then peel off the backing and press the material firmly down onto the machining bed.

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To fixture your material with hot glue, run a bead of glue around the bottom edge of the material where it meets the bed. If you use the alignment bracket, you only have to glue the sides that aren’t touching the bracket.

Note: Don’t put glue on the bottom of the material and then stick it down because this will make the material taller, which will cause your endmill to cut too deeply.

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If you’re feeling ambitious, you can remove the spoilboard, attach the material with tape, drill holes in the material that align with the slots in the T-slot bed (see Dimensions and Diagrams), and then bolt the material to the bed with low-profile M5 bolts. This provides extremely strong fixturing.

What endmill should I use when milling brass?

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 endmills.

Brass is one of the less forgiving materials, and it’s easy to break small tools with too high of a feed rate, inadequate fixturing, or simply having uneven material. The 1/8" and 1/16" endmills are very strong, and they can cut away a lot of material at once. That being said, any tool can be used to mill brass as long as the settings are correct and your material is flat. The default feeds and speeds in Otherplan do a good job of making sure bits don’t break.

What are some example projects?

Custom Aluminum and Brass Rings

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Cloisonné Enameled Metal Trinkets

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Tiny Brass Turbine

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Note: The feeds and speeds below are optimized for the V2 Othermill. If you are using an Othermill Pro or Kickstarter Othermill, you may need to experiment to find optimal settings.

Recommended Feeds and Speeds

Note: These feeds and speeds are used by default in Otherplan and are provided here as a reference.

Tool: 1/8" flat endmill
Feed rate: 7.874 in/min (200 mm/min)
Plunge rate: 0.656 in/min (16.66 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.003" (0.07 mm)

Tool: 1/16" flat endmill
Feed rate: 7.874 in/min (200 mm/min)
Plunge rate: 0.656 in/min (16.66 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.003" (0.07 mm)

Tool: 1/32" flat endmill
Feed rate: 7.874 in/min (200 mm/min)
Plunge rate: 0.656 in/min (16.66 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.003" (0.07 mm)

Tool: 1/64" flat endmill
Feed rate: 1.575 in/min (40 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 endmill
Feed rate: 1.575 in/min (40 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: Engraving bit
Feed rate: 7.874 in/min (200 mm/min)
Plunge rate: 0.656 in/min (16.66 mm/min)
Spindle speed: 12,000 RPM
Max pass depth: 0.003" (0.07 mm) Keep in mind the engraving tool has a variable width, depending on your “engraving cut depth.” The deeper the cut, the wider the tool. The shallower the cut, the narrower the tool. If you’re using an engraving tool and the generated path isn’t cutting part of your .svg file, try reducing the engraving cut depth.

Advanced Feeds and Speeds for Brass

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" endmills will break when they encounter part of the material that is sticking up. BitBreaker Mode must be enabled in order to change your feeds and speeds.

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.

To make sure you’ve got it all dialed in, face your material before milling:

  1. From the BitBreaker menu, choose Add Material Facing Job. It will come with a 1/8" flat endmill automatically selected.
  2. Set your facing depth between 0.002" and 0.008", depending on how uneven the material looks.
  3. In Advanced settings for the facing plan, change your feeds and speeds to those specified below for a 1/8" tool.
  4. If you’re using the alignment bracket and you get a collision warning, check to make sure your material height is taller than the bracket screws. If it is, you can ignore the warning. Otherwise, you’ll have to remove the bracket or move your material away from it.
  5. Start cutting!

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Once you’re done facing, your material thickness will be automatically reduced to compensate for the material that was removed.

Tool: 1/8" flat endmill
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 endmill
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 endmill
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 endmill
Feed rate: 30 in/min (381 mm/min)
Plunge rate: 1 in/min (25 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.001" (0.02 mm)

Tool: 1/100" flat endmill
Feed rate: 5 in/min (127 mm/min)
Plunge rate: 0.5 in/min (12.5 mm/min)
Spindle speed: 16,400 RPM
Max pass depth: 0.001" (0.02 mm)