I have used in the past Routers and Air Cooled Spindles and both were very noisy. I also have used Water Cooled Spindles/VFD which are silent but the smallest I could get was 800W.
I would like to build a small tabletop CNC mill for hobby cuts in wood and aluminum with a small silent spindle and I think the best one will be belt driven. My available power is 110VAC, 15A.
Can you suggest one?