a .250 cutter may be OK at .050 depth of cut, flood coolant and 5 ipm 3200 rpm.

I cut 18 feet of 304 ss with a .25 carbide 4 flute at 5ipm 2500 rpm .035 doc FLOOD coolant. The tool steel will tend to harden if cut at too high an rpm and no coolant, just the heat generated cutting it will cause the edge to harden if no coolant is used.

Would be nice to know the cutter size, doc coolant feedrate rpm etc. the more info the better.