I had a hard time finding good feed and speed numbers for milling holes in plastic ABS enclosures ("project boxes.")
After a number of failed attempts, where the plastic would just melt and burr and become a mess, I found something that works for me, at least on the Desktop ShopBot at my local TechShop:
I'm using a feed of 1.0 inches per second, a plunge of 0.25 inches per second, and a speed of 6000 RPM. This translates to about 4710 SFM if I do my math correctly.
Hopefully someone with the same question as me will find this helpful, because the resources I found on Google weren't terribly helpful. Most were referencing some manufacturer website that had gotten re-organized and was missing the information...
Here's the end mill I was using:
Niagara Cutter CB430 1/16" diameter carbide end mill TiAlN coated