Folx,
When having to hog metal on smaller mills (mine is Sieg X3) you will sooner or later discover the HP limitation of our machinery.
When going with indexable EMs, cheaper variety uses negative geometry
- which requires lots of HP for decent metal removal rates. Going with "solid" EMs - carbides and likes, is pricey and EMs don't last a lot, due to lack of rigidity in smaller mills. That and the fact the RPMs on these mills don't go into the area that carbides require (stock X3 is limited to 2000 RPMs).
Yet, there's a way to hog even toughest of tool and high-Cr steels. Enter the positive-geometry inserts and indexable endmills.
The inserts have special tip design that provides for positive geometry. Unlike negative g inserts, these can only be used in 2 positions before you discard them, but man do they remove lots of metal in a hurry requiring very moderate HPs !
As always, Ebay is our best friend. I recommend looking for 3 flute
3/4 EMs. If you can get a kit (EM + 10 inserts) for under $100, it is a killer deal and will last you a long time. Do consider availability of inserts - google for replacements before bidding.When ordering inserts, order them with larger "tip" radius - these are stronger and will last much longer. For square shoulders and likes you can always do a cleaning pass with regular EM.