I am looking at milling some parts for an aluminum sheet metal punch out of mild steel or something slightly harder and need some longer end mills. Largest end mill I can chuck is 1/4" which happens to be the smallest radius I need to cut so that works out fine - I drew out the shape so the smallest radius is as large as possible to maximize end mill diameter and minimize flex.. I have some 2 flute carbide end mills but they are a bit short - cutter length of 3/4". I need at least 1" and maybe a bit more and see that 1-1/8 and 1-1/2 seem to be standard for "long" end mills. Since they are long I am concerned about flex and think 4 flute would have less flex and chip clearing shouldn't be an issue as the chip load is small.
Trying to plan the best way to do this. Shape is basically a tube with some detail on the inside of the die and outside of the punch - main concern is the die piece. Currently thinking - drill a 1/2" hole, then mill out the shape. Should I start with a shorter end mill for what it can reach and then go to the long end mill? That would reduce the chance of breaking the long end mill.
On the bottom side of the die the pocket tapers a bit so I can use the shorter end mill without concern for the shank rubbing above the cutter length and some small steps aren't an issue (although I could use a ball end mill to minimize steps in the walls).
Any other suggestions? How concerned should I be with flex and long end mills?