Plunge Milling or Hi-Feed Milling

Plunge milling or Hi-Feed Milling? That is the question! LOL!! Actually it depends on the application. e.g. A while back, at a mold shop, the customer was looking at Hi-Feed milling some molds on a 5 axis vertical spindle CAT 40 machining center. The mold was of a good size and it had heavy scale on it as the material was 15-5 PH Stainless Condition 1025. the Hi-Feed cutter was 1" x 2 flute taking .050" DOC. The customer estimated that it would take 4 hours to mill around the periphery of the mold. We brought in a 3" x 6 tooth square shoulder face mill and by stepping over 30% of the mill by .100" radial depth of cut, we were able to reduce the cycle time from 4 hours to 1 hour. Also, the customer did not have to index the inserts for the job. But it all depends.