Cutting Sheet Aluminum without Breaking Bits

Bit type and size, feed rate, spindle RPMs, and cooling are the key parameters for success with machining aluminum on a CNC. Here's advice. June 28, 2013

What is your experience cutting sheet aluminum? I have talked to my tool supplier but now need to hear what really works. Every time they give me a recommendation I get another broken bit. 4 so far today. I'm cutting letters from 0.080 5052 or 6061.

Forum Responses
(CNC Forum)
From contributor J:
It really depends on the size of the bit you are using, spindle rpm, feed rate and if you are using any cooling method. The biggest problem is really heat. Without any liquid cooling, you will go through bits. The next thing is you want your rpms to be low and feed rate to also be slow. If you can give me your numbers, I can help. I have routed aluminum before and it's a process. Also include the size router bit and how deep you are trying to cut.

From contributor M:
I use O flute bits and a mister from Grainger at 80-100 ipm and 10-11000 ipm.

From contributor D:
Do you use a mister with an MDF spoilboard?

From contributor M:
Yes, I do, and resurface after done. Don't drench it. If the job is not too big you can use a spray bottle.

From contributor Z:
We use a mister and cut with slow helix bits 20000 rpm and around 10000mm at 5mm deep per pass. Cuts great. There are a few tricks but you can achieve better edge quality than laser if done properly.

From contributor C:
We have also had the best results from O flutes, both spiral and straight flute. A Cool Gun is another way to go. It uses compressed air and separates the cool air to blow on the tool. Everyone is right, you have to keep the heat out of the tool or no one's tool will work. A lot slower feed rates and RPM and always check those collets.

From contributor M:
Remember as well the vortex is a sure fire way to do this. The key is it needs a lot of air!

From contributor T:
What is the electrospindle horsepower? RPM band (range)? Which coupling type? And the big one - what diameter tool are you using and how large are the letters? If the letters are real small and tight relevant to the cutter diameter, you may have to rethink your overall strategy (depth of cut, number of passes as well as speeds and feeds).

I have cut aluminum for over 20 years on manual mills, CNC mills and CNC routers. Quality carbide router bits are great for higher volume material removal at higher speeds and feeds, but I have had just as good luck with off the shelf lower priced end mills in a lot of applications.

If you don't want to pop for a mister, use a spray bottle and aluminum cutting fluid. Remove any bristled brushes your machine may have surrounding your router. If a hot chip gets in them, you're going to have to cut it out anyway!