Can CNC cut mild steel sheet metal?

Can the CNC cut mild steel? If not what sheet metals cut best on the CNC? I would also be grateful for any tips for cutting metal. Best bit and best work holding method …stuff like that. Thanks!

The CNC router can cut aluminum, brass, and copper. Coated O-flute upcut bits can do pretty well.

Another interesting option is diebond, aluminum cladding on both sides of a plastic core. It’s not structural like aluminum, but it gives a good appearance (arguably better than solid aluminum), showing visible thickness, mostly for appearance-based applications like signage. It’s cheaper and lighter and much easier to cut than thick aluminum sheets.

CNC routers cannot cut steel, including mild steel.

Thanks so much!

I have tried it. It did not go well. The issue is you can’t flood cool the cut. I have done engraving with a ball mill. You throw away the ball the mill when complete.

Thanks Joe! Curious though do you not need to flood cool the other metals like aluminum or copper?

Aluminum needs air to clear chips and cool the cut/cutter. Aluminum has tendency to chip weld to the cutter if it get too hot. The new airline with pneumatic valve will make it nicer to cut. Brass is somewhat similar to aluminum

The pneumatic valve will be controlled. I did some quick research about turning on the valve. I wonder if we need to make another post processor for metal. The post processor would turn on the air and turn it off after the cut.

The air nozzle has a needle valve that is helps dial in the air flow.

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I’ve cut a fair bit of aluminum. Exactly as joe says.

I’ve found a good DOC I could get when milling large amounts of aluminum is about .030. Keep the spindle speed low, but don’t lower the feed rate too much. Drill what you can out of any pattern. It’s easy to switch between bits, but plunging into the material takes forever and kills the mills.

The air makes cutting aluminum much more predictable. It provides a lot of cooling for the metal, so it doesn’t build up heat, and importantly keeps the chips cleared out. Re-cutting a chip throw a lot of force on it all the sudden, builds up heat unnecessarily, etc. Good chip clearing lets me raise the feed and speed a bit while keeping the temp down. It went from me needing to baby it to keep chips clear, make sure it wasn’t overheating, and slow down the cutting in some areas, to basically just starting the job and playing on my phone while it cuts. My endmills last so much longer with the compressed air running.

Thin aluminum sheet (.040) can probably be cut in a single pass.

I’ve found the machine has a little bit of flex to it, so don’t expect the dimensions to be spot on, but it’s close. For example, I’m milling holes with a D of .189" in 3/8" thick stock, but they are coming out to be ~.185. I’ll just give them a final pass with a reamer when I’m done. But only being off 020 on that kind of machine with materials above it’s design spec… is really good.

Danny got me into the O-flute upcut mills, and they work wonders in aluminum.

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Specifically I think the coated o-flutes are going to be necessary. It’s supposed to harden the edge and protect against welding chips onto the cutter

Coated o-flutes are still pretty cheap

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Thanks so much everyone. This is great advice.

Here is an engraving done on the router

Looks nice!