[acannell]

I'm hogging out a 1.8" diameter, 2.5" deep hole in 6061-T6.

The mill is 2hp with a maximum torque of about 30 in/lbs and a max rpm of 7000.

Right now I can run a HSS, 1" dia, 2 flute, square centercutting end mill at around 3000 rpm to do it.

I have the toolpath spiral down at about 17ipm horizontal and 0.5ipm down.

I use air as coolant because my flood coolant system is low pressure and cant get down in there (the end mill just pumps it out).

The machine comes very close to stalling and sometimes does, the air coming out of the hole is, i'd say, hot.

I'd like to buy another end mill for this. I would think that the one I'm using is A) fairly dull..it was used when I got it B) probably not the absolute best choice for this cut.

I dont think there is an issue with the end mill I'm using chattering or any rigidity issues with the mill or setup. The issue is simply the power required for the cut.

Is there a better end mill geometry for this? I can pay up to $50 for something, used is okay (probably mandatory).

Its a cast iron mini mill, with a 10 x 7 x 10" envelope.

How about helix angle? Maybe 3 flutes would be better? Any particular brands that would be extra-sharp? What about the end-geometry (gash and all those funny angles).

Or how about a centercutting hog mill? Or maybe a bigger or smaller diameter?

Just trying to find the "sweet spot"..any help greatly appreciated!!

If I can cut power requirements by 25% that would be huge!

[acannell]

a little more thoughts:

I'd prefer something with a 3/4" shank, preferably undersized (so the flutes end up being bigger). This allows more air to get into the hole.

I am not sure if more flutes = better or worse..the machine doesn't have enough power to straight plunge any faster than about 0.5ipm with the 2 flute. Any faster and it stalls. Any slower and it chatters because its barely cutting anything and cant dig in.

BTW I've already made toolpaths that pre-drill the hole to reduce the amount of material. It doesnt help very much and takes up alot of time. I really want to get a better end mill if possible.

[acannell]

well I'll answer my own question..I happened to have a ~1" dia 5 flute roughing end mill, I ran it at a 2 degree ramp and it was doing 20ipm @ 2/3rds the current of 12ipm @ 2.6 degrees with the 2 flute..so I think thats the way to go