Looking at milling with some 3/16 to 1/2" end mills and some profiling with ball end mills. Looks like AlTiN coating is not a lot more. About $11 for carbide 3/16 ball end mill and less than $2 more for coating. Is there any down side to the coating? I am guessing it would not be good for Aluminum and some other materials. Just a hobby shop so would be good to be able to use them on different materials but the 4140 project is significant so other use is not a big factor.