monster mill(mm2) has their first gap around .60", crankenstein(3e) uses .70". The second gap is adjustable on both, 0" to .65" on MM, .1" to .7" for CS.
For harder material you would need more specialized (harder) tools. If this is just a one time project it's probably not worth buying cobalt, and would be easier/cheaper just to put a different finish on it. Maybe sand blast/steel bead it or dremel some grooves into it.