Am I expecting too much from my pm940?

I have a 940CNC and there is no way I would attempt that cut.

As it was stated above, the numbers you're pulling from the spec sheet are starting point numbers for industrial machines that probably weigh in excess of 10k lbs (if not MUCH more). No way you are going to touch those numbers with a standard knee mill, much less a hobby bench top. .4" DOC x .1" WOC x 30IPM = 1.2^3 MRR. That'd be a lot in aluminum for your machine, much less hardened steel.

That being said I have cut .25" DOC and .05" WOC very reliably in steel using a 3/8" carbide 4 flute endmill. Finish pass was 0.75" DOC at .010" WOC. Parts came out looking amazing.

PZ
 
I have a similar end mill that I use on my PM-25. That one really does not like a large DOC. I know that in theory, you should be able to cut as deep as the insert goes, but I have similar vibration issues anytime I go above maybe .2" DOC. I usually run that one around .1" DOC and increase the WOC. Traditional end mill do much better for me if I want to take a larger DOC.
 
I also I have a Shars APKT indexable endmill (3/8" single flute flavor) and have found it to be too rough on my G0704. It worked OK on the very large knee mills I had at school, but I have given up using it on a benchtop. One issue is that the inserts aren't very sharp. This is OK on big machines with a lot of spare HP, especially since it helps with tool life, but really creates a LOT of cutting forces. If you want to machine aluminum, consider trying the APGX insert. It should fir your same tool but has a razor sharp ground edge for non-ferrous metals.

But to echo what was said above, use a corncob roughing endmill for bulk material removal and some good carbide solid endmills for everything else.
 
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