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Breaking endmills in G-Wizard--what's wrong?

Well I finally got a chance to use the suggested feeds and speeds I got from my G wizard trial. I was pretty excited but that did not last long, I broke three .125 end mills before I gave up.
I really dont know what I did wrong. It gave me a feed of 40ips with depth of cut at .053 and plunge rate of 13.3ipm using a 3 flute carbide end mill with .75 stick out. Snapped them like twigs every time. I turned down the feed rate to 9ipm and it seems to help, but how could it be so far off? 
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I see from your screen shots and other information you’re on a home built CNC router.  Those are pretty unforgiving.

The G-Wizard feeds and speeds should work for you IF EVERYTHING ELSE IS JUST RIGHT.
So what else can be going wrong?
First, you should go through my post on cutting aluminum with routers:
My suspicion is that you probably do not have an effective way to clear the chips (compressed air blast or flood coolant) and are probably not using any lubricant, such as a mist.  This makes it really tough to cut aluminum because it tries to weld itself to the cutter.  The best ways to minimize this in order of how well they work are:
1.  Lubricant, usually mist in the air blast.
2.  clear the chips so the cutter is never recutting the same chips.  This usually requires a powerful air blast.
3.  Use a special coating on the cutters.  This is not recommended, but you can try TiN and TiAlN cutters.  They’re more expensive and will still fail if the coating gets worn off.
One more thing to consider.  Unless you have a fairly expensive spindle, you may be suffering from too much runout.  See this article for more:
This seems fairly likely.  If you can’t find a way to minimize the runout, you’ll need to reduce your chipload quite a bit.  Too much runout will limit how small a cutters you can run pretty severely.  Unfortunately, there’s a reason good spindles are so expensive.
If we were to eliminate the lubricant/chip clearing issue and the runout issue, the last thing to consider is using fewer flutes.  Some aluminum is gummier than others and just needs more chip clearance.  Try a 2 flute instead of a 3 flute. In really gummy aluminum even a 1 flute may be necessesary.
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