I started milling out the pockets of the part I'm working on with @jaelen_hsu.
It all started pretty well; I didn't make any changes to the original program I set up and set it off running. It got through the first three pockets no problem, however, when it got to the fourth one, the 1/16" endmill I'd been using, snapped! I had it running at 24 in/min, 10% sideload, and 100% tool diameter step-down (0.0625"). Thankfully I caught it on camera and found that the issue was due to chip welding, what I'm confused about is why it didn't break before, the sound was pretty much the same throughout and no noticeable chatter.
I decided to speed it up to 30 inches a minute and lowered the sideload to 8%, and stepdown to 80%, and the same thing happened, it ran for a minute or two, then snapped as well. The only other thing I can think of that is happening is lousy chip evacuation, and the endmill is recutting the aluminum and bonding onto it.
If anyone has any idea as to how to fix this issue, I'd greatly appreciate it! I'm down to my last 1/16" endmill and don't want to try anything I'm not pretty confident with.