Cutting Stainless Steel

Hi I need to cut a pattern out of 1.5mm stainless steel with my lowrider. The first attempt I had ended in dramatic failure with my 3mm cutting tip getting red hot and nearly starting a fire. I would be grateful if some one could advise what is the best tool and speed settings would be to cut 1.5mm stainless with a 2 to 3mm cutter? Thanks in advance.

Take it somewhere and have it laser cut. Stainless is a pain to cut on big mills.


Agree with Barry but if its really really really is not an option.

Airblast or some coolent (preferred) to keep the end mill cool, and trochoidal milling with a shallow depth of cut may get you there.
Shallow and slow with minimal tool force is the order of the day.
And try to find a stainless steel alloy that does not work harden.
If it work hardens, your going to have issues all over again.

You have gotten some good advice thus far. What alloy are you working with?

The best machining stainless is 303, but anything in the 300 series could work harden. 316 is the worst with this. 304 is very challenging and should be avoided.

If it is 400 series, ensure it is annealed. These can get to 50-60 Rockwell, that is almost cutting tool territory. (Surgical cutting tools are in this category)

17-4 is a good choice for machining as well. This stuff actually can cut a little BETTER when hardened as it chips better…but this depends on the exact type of machining operation you talk about. This is a more rare alloy, so I doubt this is applicable to you.

For settings, the problem here is spindle speed. Routers are just too fast. If you have speed control, you have a chance. Trouble is if you want to go slow (which you have to with a not-very-rigid machine), the speeds and feeds suggested have the spindle down around 3-4k rpm. As you go faster you make smaller chips, which can’t carry the heat away. When that happens the tool rubs from friction instead of “getting into the cut”, and I think you have seen what happens then.

Cooling (air or liquid) will be essential.

Aluminum tolerates much higher spindle speeds, which is why the mpcnc is capable of it.

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Thanks for all the great advice. For expediency I think i will get the Stainless steel part laser cut and stick to aluminium with the lowrider for now. May come back to stainless at a later date when I have more experience.