End Mill advice

[Chris64]

I've been toying around with my CNC for a couple weeks now. It's not what I was expecting. Everything requires so much planning and prep. I'm still hooked...but I really wish I had an auto tool changer...oh well, maybe my next machine. I should qualify this by saying it's just a hobby of mine (not a business) and I probably only know enough to be dangerous.

Anyway, I'm trying to understand some things about End-mills. I got a real good deal on 4-5" long 1/2" dia 4 Flute end mills...I think I know why, because I'm finding them virtually useless. They just seem to be too flexible. I get a rediculous amount of chatter from them regardless of RPM/IPM/Direction. I bought a decent carbide 1 1/2" long 1/2 2 Flute end mill and it does everything better than the other mills. It has less chatter, faster cutting and cleaner finish. What I'm doing is pretty standard, mostly tracing out basic shapes on alum & steel. Some face milling too. Well I'm happy with my 1/2 carbide for face milling until I get some tool holders for something larger than 1/2", but for cutting out an outline, 1/2 is way too big. So I've been having the best reults with a 1/4" 2-Flute. I'm confused though about somethings...it seems to me that the deepest cut I can do at any given time is about 1/8". I tried to go deeper (with a wider cutter) but at any feedrate I start to get chatter and it makes the cut pretty messy and doesn't seem any faster.

Q1) What would you guys suggest for cutting out a template in something like 1/4" thick steel or aluminum? I've considered using a plasma to pre-cut the piece and then smooth it with the mill but I don't think can free-hand plasma cut it good enough for that to be beneficial.

Q2) Why would they make a 4-5" long end mill with a cutting edge along the entire edge (minus the 1-2 inches where it mounts) when it appears that 100% of the cutting (as far as I can tell) is done with the first 1/8 of an inch. Is it just for metal clean-out? Even if you're plunging a deep hole...you're still only cutting with the very tip, right?