The lesson that should have been learned here is carbide should have long
ago been abandoned in favor of HSS and proper tool geometry.

I mostly use HSS toolbit because they work for me. I remember one time
I was machining 4140 and have a tough time of it. My experienced machinest
friend told me. Sharp HSS with a surface speed of 50 and lots of lube.
I use that combination for most steels with good success.



Mild steel, which appears to be the topic of discussion, is amongst
the worst of materials to machine in that it loves to tear.

Machining garden varity CRS will make you buy 12L14!



416 is also a free machining
grade, and is capable of heat treatment, should you have need.

I think you need 440 for heat treat.