7 Essential Tips for Successful CNC Router Aluminum Cutting

cnc router bits for cutting aluminum

People often ask whether a CNC router can cut aluminum, as they typically see it used for cutting wood and plastics. My answer is always, “Yes, if you do it right.”

CNC router machines are suitable for fabricating with wood, plastic, aluminum, and more. However, there are a few key differences to remember when working with aluminum compared to wood or plastics. 

  • First, aluminum has a much smaller “sweet spot” for optimal feeds and speeds. Straying from this sweet spot can result in cutters breaking, wearing out much faster, and producing poor surface finishes. Additionally, there are multiple sweet spots depending on the specific task. Metals, in general, have much narrower ranges of acceptable feeds and speeds than wood or plastics.
  • The second thing to consider when working with aluminum is its “stickiness” factor. Aluminum tends to stick to the tool, sometimes to the extent that it welds itself to the cutting edges. Once gummy aluminum deposits form on your cutting edge, the tool’s lifespan is significantly reduced, especially at high speeds of 20,000 rpm or more.

router bits to cut aluminum

Despite these challenges, you can successfully cut aluminum on almost any router. 

Here are 7 tips for CNC router aluminum cutting success:

1. Don’t Rush

A CNC router machine can cut aluminum, but it isn’t ideal for hogging out large aerospace parts like wing spars. To succeed, you need to be patient. This doesn’t mean slowing down your feeds and speeds, but rather accepting that your overall material removal rates will be lower compared to a purpose-built CNC mill. Relax and let the machine do its work. One advantage of a good-sized CNC router is that it can hold more material on its table than most CNC mills. Load it up, press the green button, and walk away

2. Use matched Feeds and Speeds

One challenge with most CNC routers is that their spindles run much faster compared to CNC mills. While a typical CNC mill maxes out at 10,000 rpm, many CNC routers start at around 20,000 rpm. The next couple of tips will focus on solutions to address this issue.

router bits for aluminum cutting

3. Use carbide-coated router bits for aluminum cutting

One way to bump up the recommended rpm is to be sure you’re using cutters that are happy going that fast. The measurement that determines this is called Surface Speed (for more on this and many other feeds and speeds hints and tips). Carbide cutters can go much faster than HSS cutters. Forget HSS and Cobalt for the most part. A coating, such as TiAlN allows the cutter to go even faster. Shop for carbide TiAlN coated cutters. They cost a little more, but they can change your results so much it’s darned well worth it.

For example, suppose I need to cut a slot using a 1/4” endmill. If I select an HSS endmill, G-Wizard recommends running it at 5877 rpm, but my 20,000 rpm router spindle can’t go that slow. By switching to a TiAlN carbide endmill, the recommendation changes to 16,897 rpm, which is much closer to my spindle’s speed. This is based on a Surface Speed of 1106 SFM. You might find more aggressive SFM recommendations from your tool manufacturer. With aluminum, I’d go ahead and try 20,000 rpm for this cut; it’ll likely work just fine.

4. Use smaller diameter CNC router bits

The other way to bump up the rpms is to use smaller diameter cutters. Forget about 1/2″ endmills. Drop down to 1/4″ maximum and typically less. Because you’re going to smaller diameters, you want more rigid cutters lest tool deflection starts to be a problem. Carbide is much more rigid than HSS, so this is one more reason to favor carbide.

The moral of the story is to carefully match your tooling to the capabilities of your machine.

router bits for cutting aluminum

5. Lubricate with a Mist

Provide lubrication to cut down on the tendency for the chips to stick to the cutting edges. You pretty much have to use some kind of lubricant. In fact, buy a mister to provide air blast and coolant mist. It’s easy and inexpensive.

Sometimes, it just isn’t possible to use mist but you still need to cut some aluminum. If you’re cutting very thin aluminum, or taking very shallow passes, you may be able to get by without lubrication. Do some tests and see.

6. Don’t slow down the feed rate too much!

If you go too slowly on your feed rate, you run the risk of making your tool rub rather than cut. This is a much bigger risk for CNC Router users than mill users simply because the spindle is going so fast. To maintain recommended chip-loads with rpm that high you’ll have to keep the cutting moving smartly. Our 3/16” cutter at 21000 rpm wants to feed at 91 IPM, for example. If you slow down too much, say to 1/4 of that, many will think they’re babying the machine and tool. Nothing could be further from the truth. If you wind up going slow enough that the cutter starts rubbing at 20K rpm, you’re going to heat up the whole work and drastically shorten your tool life.

Aluminum cutting router bits

7. If your CNC machine can’t feed fast enough, use fewer flutes and increase cut width

Normally, we use 3 or fewer flutes with aluminum anyway–don’t try a four or more flute cutter in aluminum! The reason is that aluminum produces especially large chips. The fewer the flutes, the more space between the cutting edges, and the more room for the big chips to escape and be blown away. With too many flutes, the chips back in too tightly, jam up the flutes, and pretty soon you have a broken cutter.  

By following these tips, you can significantly improve your CNC router aluminum cutting projects, achieving better quality, efficiency, and tool longevity.

Conclusion for CNC Router Cutting Aluminum:

Machining aluminum with a CNC Router is absolutely doable with most any router. It’s just a matter of matching your machine’s capabilities to the “sweet spot” feeds and speeds requirements of the material through the wise selection of tooling and cutting parameters. 

If you are interested in CNC router bits for different materials, feel free to contact us. More information will be provided upon request.

cnc router bits for cutting aluminum

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