Hello, I am new to this forum and generally to cnc machining. So I am in process of building my first cnc, and I have a question about end mills. I need to drill/plunge different size holes in 6061 aluminium, my spindle is 2.2kw Chinese water cooled, so I can go up to 24k rpm, but that's not really the case as I need to drill 8-20mm holes in 16-50mm depth. If I am not wrong these chinese spindles can go as low as 1k rpm. The idea is getting something like 8mm carbide 2 flute drill bit and drill a hole slowly (~1k rpm), then change it to 8mm carbide 2 or 3 flute end mill, that will widen the hole size up to 20mm.
Is the right approach and where to buy these end mills?
P.S. I will be drilling shit loads of holes so I need something lasting.

Thank you, any tips will be much appreciated.