I am not sure how much power you have.
But for drilling 1/4" I usually go 5000 rpm and 45 IPM in aluminum.
Yes its 45.0 not 4.5!
Using flood coolant and peck every 0.2" for regular drill.
You can drill 10x deep easy.
Reduce your cutting speed if you have not enough coolant.
But drilling is nor really required.
You can do everything with just a 1/2" 2 flute carbide endmill.
Helical interpolation works well.
We go 5000 rpm 60 IPM Widiah a ramp angle of about 2.5-3 degrees.
Again you need a way to lupricate and remove chips.
Aluminum does not like to be cut dry.
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