Machining 304ss with carbide endmill

[nybuxt]

I am having problems machining 304 stainless using a carbide endmill. I am burning up and /or chipping the flutes.
In particular this is what i am trying to do; I am machining pockets in 3/4" stainless, approx. .100 deep steps to a depth of .600 using a 4 flute 1/2" carbide endmill. According to the specs I have found , I should be running 200-350 SFM at .002-.0025 chip load per tooth.... this according to my calculations is about 1500rpm at 14-15 IPM. I've tried varying my RPM and feedrates and just can't seem to get anything that works right. I'm told that i can run the RPM much higher but seem to get more chatter and harmonics. I'm using flood coolant, on a large ,very rigid CNC machine so I know it's not the machine flexing. I am ramping the cutter into the work rather than plunging. In the past I was doing similar work using a coated HSS cutter, using the cutting specs supplied in the Mastercam mill library, ..it worked fine but took hours because of the slow RPM and feed rates....thus the reason for wanting to use carbide.( Mastercam doesn't seem to have any specs in the tool data base if you tell it your using carbide rather than HSS)

Any suggestions??? I'm getting tired of wasting endmills.

[little bubba]

First, what type of endmill are you using and are you running wet or dry. I'm going to guess from your description that you are using a standard 4 fluter and are running wet.

If you are running a standard 4 flute finisher, ditch it, finishers are for finishing. They are not the tool to use to remove a bunch of material, and can make some nasty noised when you bury them, and it can shake even the biggest machines.

I would go with either a carbide rougher or a variable flute endmill, preferably TiAlN coated. I'd start at around 250SFM .002 to .003 per tooth, dry, with an air blast. Probably run even deeper with almost 100% stepover.

[Konrad]

I would drill out as much as you can, then rough out with HSS roughing milling cutter at full depth, finish with carbide.
Konrad

[AMCTony]

I would use a Seco Nano turbomill. They come in 1/2 and 3/8 inch and use inserts. This should give excellent material removal rates. Can you switch to 303 stainless?