Wanting to get some advice in using cobalt tools in 4140 and 4140 PH. Mainly interested in the PH as the other should be easier. Have some cobalt drills and will be running them on a machining center with coolant. Is that sufficient or should I be thinking of cutting oil? Peck drilling of course. speeds and feeds?

Another question is roughing end mill - I have a 1/2" cobalt roughing end mill (uncoated). Is this reasonable to use on the PH or is it going to have a short life and I should go to carbide?