I often cut steel on the Shapeoko and in fact, I spent most of the day today cutting some 1018 low carbon steel (Ref 1.25 dia). I was boring 5/8" holes in 1.0 inch long slugs and milling a 7/8 C’Bore 1/8" deep. Major cutting tool manufacturers will list the cutting rates for their tools for a general range of material. (HSS, Carbide and Coated Carbide, etc.)
For example, 303 Stainless steel my reference chart says 150-200 SFM. I ALWAYS try use the lower number to start.
So using an online SFM Calculator a 1/16" end mill at 11,000 rpm = 170 SFM.
So this one number tells you the important info. Spindle speed for a particular cutter diameter.
Feed and Depth of cut? I like what I call the 10/10 rule for steels. Feed: 10 in/min. DOC 0.010" (Starting Point)
Following these guidelines, I can easily get a full day out of a cutter, or if I use the higher number…about a half-day. It’s what I’ve use for 40+ years of machining and 5+ years on my Shapeoko.
Questions?
Oh and for the cutter lubricant?.. (Eg: steel and 303 stainless) WD40 using my Drip Can method OR Oil-soluble coolant.