I've heard the rule of thumb that I should plunge at my normal feed rate divided by the number of flutes on the end mill. So for a 2 flute cutter, I should plunge at 1/2 the normal feed, for a 4 flute, it would be 1/4. etc. But my question is if the "normal feed rate" is the feed rate that I would use for a 25% radial depth of cut (such that 25% of the end mill's width is used), or for a 100% radial depth of cut (as when slotting)? In other words, if the manufacturer recommends 10 ipm at a certain RPM and 25% cutter width, do I plunge at 10/4 ipm or 10/4/4? Thanks,
John