Feed rate help

[churchjw]

I am having problems figuring out the feed rate for a cnc mill. Any help would be great.

Starting with RPM. I am using the formula RPM = Feet per Minute/Pi*cutter diameter

So for a .500 carbide 4 flute mill cutting Aluminum Using a FPM of 900

That gives 573 = 900/3.14*.500

So 573 RPM

Then for feed I am using Feed rate in Inches Per Minute(IPM)= RPM x number of cutting edges x chip load

Using a chip load of .004" I took that value from http://www.endmill.com/pages/training/Speed and Feed - Carbide End Mills and Drills.pdf

That gives 9.1 = 573 x 4 x .004

9.1 IPM can not be right can it? Where am I going wrong?

 

[Tony Wells]

Hmmm.....lessee, how many inches in a FPM?

 

[churchjw]

Oh God is it that easy.:banghead::banghead::banghead::banghead:

So that would be 6878 RPM = 12*900/3.14*.5

110ipm = 6878 x 4 x .004

That sounds much better. Is it right?


Thanks Tony you are a life saver.
Jeff