So this thread quickly went to bashing tool vendors as not knowing what they are doing.... There can be some truth to that statement. But that usually depends on who in that organization you are working with.
Even for a 1/2" Harvi 1 TE, .002 IPT is on the high end for slotting, no less plunging. Not saying it can't be done, but generally speaking I recommend 40-60% of the slotting feed for straight plunging or aggressive ramping. Especially in a weak setup such as a live tool holder. I am guessing the endmill was overloaded chip load wise due to the live head not keeping up RPM wise. So you ended up with an even higher chip load which ended up being a viscous cycle generating more chip load until failure.
Cut the feedrate until it works, it will be fine at the depth you are going to. I'd start around .0008"-.0012". Don't be afraid to use some short pecks, but don't retract more than the chip load. If you interpolate it/ramp it, unless you can get near 2xd in hole size, it won't make much difference other than now you will be putting side load on the tool as well, the biggest difference that it will make is if you have a shallow helix angle, essentially it is just reducing the effective z feed.
Best of luck.
