[machintek]

I used to cut microwave parts from aluminum using mist coolant, typically with OSG aluminum high helix 2 flute end mills of .500 diameter. Usually 1/2 inch deep and almost full width per pass using about 2450 RPM and about 25 IPM. This was back in 1987 on a BOSS 9, R2E4. Try turning down the feedrate and as it is cutting, turn it up. The hardest part for me (this was my first CNC) was to take what I had felt, heard, saw, and smelled as a manual machinist and give it numbers for the CNC.
When I wrote a program, I would adjust it as it ran and made notes. part done, the changes were applied to the program, and the program was saved as a finished working program.

George

[afmcorp]

hello

first u didn't mention if ur tool is coated or carbide or? so let me assume that u r using HSS 4flt CC. to determine speed & feed u need to determine what is the SFPM u can go [lets start at 300 sfpm] next u need to know what u can load each flute i.e. .003 / rev using these 2 numbers for a .500 endmill we find the following:

RPM : 2291.83118
FPM : 300.0
IPM : 27.501974
IPR : 0.012

so u need to run 2300 rpm with a ipm of 27.

u need to study up on this issue. i suggest u go to niagara's website and down load their charts. next buy the machinery's handbook. i'd also go to other mfg's of endmills etc: to get their take on speeds and feeds.

one more thing you will find. as ur depth increases your feed rate will drop. then u'll learn the old gut feel of what's too much and then u'll be tuning the endmill by sound. if it's a sequealling your just polishing the metal. remember the chip is to remove heat from the tool and work. also the various coatings available can effect your speed and feed by 25% and more. one more thing especially true with aluminum is to keep the flutes clear. i use a massive amount of air blowing on the tool so the chips will evacuate the flutes. if the flute is full when it comes back around to make the next cut where is the new cut chip going to go. right .... nowhere and pop u have a brand new broke tool.

just takes time and practice. i had no one to show me how so i learned the hard way by breaking tools. as i got more experience i had less broken tools. if u can find someone [shop] willing to let u stand around and watch do it. u'll learn alot.
good luck