DIY CNC machine for steel?

[Boyan Silyavski]

Hi Luke,

I see you have been impressed by other peoples videos where they cut steel on their routers. So lets cut the crap- the answer is:

If you want to properly cut metal- buy or make a proper metal cutting machine.



Detailed, i write this down for the benefit of others in the future that drop here with similar questions:

-with the machine you have drawn would be next to impossible. Forget aluminum, all need be steel, all needs to be braced in all directions, the thicker and the heavier-the better. You could use aluminum, but must be reinforced with steel.

-The spindle.
There is cutting, there is what we call scratching. This spindleis NOT made for cutting steel. Means bearings will fail at one moment. These bearings have 1 year life if machine working 8h a day. Thats what Chinese manufacturer states. And that routing wood. Many people, including myself have used them much more and on materials like aluminum.

The ideal spindle for a small machine to cut metal is the BT30, coupled with pneumatic release for tool change and belt driven by servo motor. Thats about 2000$ from China. If you weld and have a machine shop you coul dput together a frame. They /China/ sell a very nice VMC frame for that setup but is expensive. Thats one of the reasons you will not see many DIY mills in forums. Cause its cheaper and better to buy and retrofit old mill.

-the power needed
One thing worth noting is that yes, if you have very sturdy setup, use small bits, have rigid table, proper cooling and calculate properly speeds and feeds you could machine mild steel. I dont see how thats to happen if you dont use some software like HSMAdvisor or Gwizard to finely calculate what exactly you are doing. From there you will see the forces involved and the power needed to do that.

I myself use HSMAdvisor, inside there is an profile of 3kw 18k rpm spindle, use that to see what happens. I highly recommend getting the 3kw versus 2.2kw for metal.
Have in mind that most spindles use all ceramic bearings or partly. There are dedicated high speed spindles for metal that cost more and they say with better bearings. I have no info if thats reality or Chinese tricks.


-the machine design
So yes, if you go that way, its better to have the gantry fixed. Do your research and see build section in forum. There are discussed machines exactly made for what you say.

-me personally
i would buy me a small mill or retrofit big one. I in fact am just finishing a very sturdy build that could definitely do that what you want, but dont plan to f__k my spindle cutting steel

Hope that helps

PS. below a snip from HSMAdvisor, As you see spindle power is not the limiting factor. it would be the stiffness. sliders are adjusted for standard stiff machine/ mill/