In case anyone is out there thinking “I might want to mill aluminum from time to time.” Go ahead and get something stronger/faster than the quiet cut spindle. It’s worked great on plywood, abs, and acrylic; not on aluminum. You know…in case you want to mill a Z-axis upgrade for your SO2 that isn’t available for sale.
I ran a 1/8" single flute steel upcut at s8000 (8000 rom, max on the quiet cut). Rate was 0.04 in/rev or 4 in/min feedrate. Aside from the pains of re-zeroing mid-cut due to a broken bit, I had problems with endmill chatter, plunge variation from mount slippage, and z-axis wheels loosening.
My piece (read: second attempt) isn’t usable because some of the circular patterns didn’t come out true. The bearing isn’t centered or well supported. This was most likely because of drag on the machine. So we’re my plunge issues. Sure, I could’ve slowed down even more…had I known they were off I would have. Even so, it was a 1:40 job.
I’m just going to stick to softer materials until I come across a palm router.