Basically Excel or the free Open Office Calc program are extremely powerful Calculators that are once setup are easy to use. There is no need to buy anything, just find a computer to use. If you do not know what Excel is basically don't bother reading any further.
I created a basic Excel file that takes basic sfpm of machining Aluminum, Steel, and Stainless and Entering Endmill diameter gives feeds and rpm and depth of cut for various length end mills. It automatically does the calculations of course.
Rough estimates of maximum possible. Obviously with a short Stub End mill much higher feeds are possible. Basic Engineering is end mill sticks out 1/2 length it is 2x2x2 or 8 times more rigid and usually can handle easily 4x the feed of a regular length end mill.
This is assuming a Rigid and high horsepower machine with a rigid clamp / vise setup.
1/4" HSS EM 2 flute aluminum feed 4.6ipm at 0.025" DOC
1" Carbide EM 6 flute Stub length in aluminum feed 220ipm at 0.100" DOC
..... this is my point, by using a Short Stub length End mill with more flutes.....the Feed and Depth of Cut possible increases a very very large amount.
......That is if your machine has the Horsepower, Rigid enough not to chatter, and you can hold on to the part being machined AND you can flush the metal chips out of the way.
...... This is my main point very rarely does a feed and speed chart ask for the length of the end mill. This I consider the Most Important Question to ask first....... Too often machinist are cutting at less than 10% what is possible because they are using a long End mill rather than a Stub length one.
....... Check the Excel formulas used and adjust them if needed. Your results may vary. Do not use
1) if you do not take safety protection into account. Safety guards need to be able to stop a breaking end mill traveling at high speeds. If you do not use guards around end mill do not try pushing the speeds and feeds to the max.
2)Watch out for stalling the motor and over heating the motor.
3)Bearing and other machine damage may also occur.
.......the attached free Excel file will calculate Speed, Feed, and depth of cut for Stub, Regular length, Long End mills after entering end mill diameter and number of flutes
.......there is a factor which can be entered / changed that effects depth of cut and feed. obviously long end mills cannot handle as high a feed as a shorter one. in general a cutter 2x longer will deflect 8 times more. cutter length effects machining limits enormously.
also gives cubic inch per minute removed which is an indication of horsepower requirements. obviously it takes more horsepower to machine Stainless compared to Aluminum.
also worksheet shows how side milling or radial milling is faster as a faster rpm / feed can be used because of better cooling of cutting edges
using a computer to do the math can increase speed of machining often by 10x what a machinist thought was the fastest. Basically when using a CNC only feed override is used for throttling down from maximum do to chatter or machine spindle stalling out. Of course the part needs to be held in a vise strong enough not to get pushed out of position.
..... don't use Excel calculator if you will not take safety precautions from possibly breaking end mills, parts moving in vise, motor stalling out and burning out and or damaging bearings, etc. use at your own risk and verify all suggestions that the Excel feed and speed calculator gives