Anyone have feeds and speeds for mild steel facing ops?

I would like to face some mild steel rectube im gonna be using for another smaller cnc and im not sure where to start. Ive only ever milled 6061. I will have 1/8th inch two flutes, 1/4 inch 3 flutes, 4 6 and 10 mm dlc coated three flutes when the time comes around to be ready to do this project. My machine is setup for iso mist but cant change the coolant if need be.

I’m not sure which router you are using so I will assume the lowest RPM you can do is 16,000. Based on that, the largest end mill you should use is 1/8". Much larger and you exit the recommended surface footage range of solid carbide in low carbon steel. On an 1/8" 2 flute, you can start at .0004" per tooth feed rate. Your axial depth of cut should be around .040" with a step over of .020"

So, 16,000 RPM at 12.8 IPM to start. You can bump it up gently from here if need be but start slow. I’m not sure that I would use iso but maybe a cutting fluid designed for this application.(fire hazard)

My recommendations were based on what you have available to you at the moment. If it were me, I would use an end mill designed for cutting steel. The ones you have are designed for wood, maybe plastic. Not all carbide is the same and flute geometry is very different. I would use a 4 flute something like this. Harvey

One last piece of advice, contain the chips the best you can. Don’t blow them around. Your rails, belts, ball screws and electrical components are not very well protected and metal fragments can have a very adverse effect. These machines were designed to cut wood and at best non ferrous materials. (forgive me Kevin) Just because you can, doesn’t mean you should.


Down at the min 8k rpm for a 1/4 cutter you are just over 500 sfm which works fine for steel. A nice 4 flute carbide should work fine at 32in/min to get you .001 chip per tooth. As soon as carbide3d gets my spindle electronics issue resolved I’ll run some tests to see how far you can push it,

Also, use a stub end mill to help with rigidity. I’ve hade good luck with lakeshore carbide stuff