Newbie Correct drill bit for Aluminium

I'm attempting to drill and ream holes in 6mm Aluminium on a Chinese CNC router.

I'm drilling with a 3/16 drill (4.76mm) and then reaming with a 5mm reamer.

I'm using a very slow feed -- 12,000 RPM and 20mm/minute, but find that I get a lot of vibration, and my holes end up oversize.

I've measured 0.02mm runout at the shank of the bit.

The drill bits I am using are these: NEW 3 16" 1875" Printed Circuit Board Drills PCB | eBay

Are they suitable? I wonder about the 1/8" shank,

Would I get better results with something like this: 3 16" Diameter Stub Black Oxide High Speed Drill BIT 135° Point USA RMT 95001868 | eBay ?

Thanks for any suggestions.